Liquid-crystal display element

ABSTRACT

An object of the present invention is to provide a liquid-crystal display element using a liquid-crystal composition having negative dielectric anisotropy, capable of realising excellent display characteristics by being used in an FFS mode liquid-crystal display element, without deteriorating various characteristics as a liquid-crystal display element such as dielectric anisotropy, viscosity, a nematic phase upper limit temperature, nematic phase stability at low temperatures, and γ1, and burn-in characteristics of a display element. A liquid-crystal display element containing at least one compound selected from the group consisting of compounds by the following General Formula (I) is provided: 
                         
wherein each of R 1  and R 2  independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, A represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group, k represents 1 or 2, and in a case where k is 2, two A&#39;s may be the same as or different from each other.

TECHNICAL FIELD

The present invention relates to an FPS mode liquid-crystal display device using a nematic liquid-crystal composition having negative dielectric anisotropy, which has high transmittance and a high opening ratio.

BACKGROUND ART

From the fact that display quality is excellent, active matrix type liquid-crystal display elements have been pot on the market for portable terminals, liquid-crystal televisions, projectors, computers and the like. In the active matrix type, TFT (thin film transistor), (metal-insulator-metal), or the like is used for each pixel, and it is important that the liquid-crystal compound or the liquid-crystal composition used in this type has a high voltage holding ratio. In addition, a liquid-crystal display element obtained by combining a VA (Vertical Alignment) mode, an IPS (In Plane Switching) mode, and an OCB (Optically Compensated Bend, Optically Compensated Birefringence) mode to obtain wider viewing angle characteristics and an ECB (Electrically Controlled Birefringence) mode reflective liquid-crystal display element to obtain a brighter display have been proposed. To cope with such a liquid-crystal display element, currently, proposals on a new liquid-crystal compound or liquid-crystal composition are made.

At present, as the liquid-crystal display for smartphones, a fringe field switching made liquid-crystal display device (FFS mode liquid-crystal display device) with high quality which is one type of an IPS mode liquid-crystal display element excellent in visual characteristics is widely used (refer to PTLs 1 and 2). The FFS mode is a mode introduced for improving the low opening ratio and transmittance of the IPS mode, and as the liquid-crystal composition used, a material using a p-type liquid-crystal composition having positive dielectric anisotropy is widely used from the viewpoint of easily lowering a voltage. In addition, since most applications of the FFS mode are for portable terminals, more power saving is strongly demanded, and liquid-crystal element manufacturers are continuously performing active development such as adoption of array using IGZO.

In addition, as the alignment method of the liquid-crystal molecules, a method called a rubbing method is widely used. In this method, by rubbing the surface of the alignment film in a certain direction by rotating a roller wrapped with cloth such as nylon or the like with respect to a thin film obtained by applying art alignment film material such as polyimide and firing the applied material while pushing with a constant pressure, an alignment restricting force is imparted to the liquid-crystal molecules. The exact alignment mechanism at this method, is still not clear, and since there are problems that streaky display unevenness occurs by rubbing the surface of the alignment film, a part of the alignment film material falls off, and then, is mixed into the liquid-crystal layer, and TFT is destroyed by static electricity generated in the array substrate, an alignment imparting method in which rubbing is not performed has been studied. In particular, since alignment can be imparted in a non-contact manner with respect to a photo-alignment film obtained by imparting anisotropy to an alignment film by using ultraviolet rays linearly polarized, development of the photo-alignment film has been progressing as a method for solving the problems of the rubbing method, and the use of the photo-alignment film has been sought even in a horizontal electric field type display element (refer to PTL 3).

CITATION LIST Patent Literature

[PTL 1] JP-A-11-202356

[PTL 2] JP-A-2003-233083

[PTL 3] JP-A-2013-109366

SUMMARY OF INVENTION Technical Problem

When comparing the VA mode and the FFS mode, both are significantly different in all, of the electrode structure, the direction of alignment, the orientation of the electric field, and the optical properties required. In particular, since the FFS mode liquid-crystal display element is characterised by the structure of an electrode, there is no knowledge regarding the problems that the effects will be difficult to be predicted from the techniques in the related art, as burn-in or drip marks. In addition, the IPS mode and the FFS mode are in common in the large category of the horizontal electric field type, but are different in the electrode structure, the direction of alignment, and the orientation of the electric field. Accordingly, in the case where the liquid-crystal composition used for VA is simply used in the FFS mode, it is difficult to configure a liquid-crystal display element having high performance as is demanded these days, and an n-type liquid-crystal composition optimized to the FFS mode using a photo-alignment film has been demanded.

In addition, as described in PTL 1 or 2, since, an FFS mode electrode has a structure in which a plurality of strip shaped electrodes formed on the substrate surface are arranged in parallel and the entire surface of the substrate surface is covered with the alignment film, in the case of arranging the liquid-crystal molecules the longitudinal direction of the strip shape electrodes as the liquid-crystal display element using a p-type material, the longitudinal direction of the electrodes and the rubbing direction of the surface of the alignment film are parallel, and thus, rubbing irregularity is low. On the other hand, in the liquid-crystal display element using an n-type material, it is necessary to arrange the liquid-crystal molecules perpendicular to the longitudinal direction of strip shape electrodes, and it was confirmed that, it rubbing is performed perpendicularly to the longitudinal direction of the electrodes, problems that rubbing irregularity is inevitably increased due to unevenness of the electrode, and an alignment restricting force with respect to the liquid-crystal molecules is significantly reduced, occur.

Furthermore, in PTL 3, it is described that, when an electric field is not applied, the liquid-crystal molecules are aligned by a photo-alignment film in which an acute angle α between the long axis direction of the liquid-crystal molecule and the direction (x-direction) of extension of the scanning signal lines is 75 degrees to 88 degrees, and if a potential difference is applied between the pixel electrode and the common electrode, an electric field (so-called horizontal electric field) which mainly has a component parallel to the liquid-crystal layer with respect to the substrate plane (xy plane) is applied, and thus, the long axis direction of the liquid-crystal molecules of the liquid-crystal layer is arranged along the electric force lines. Therefore, it is possible to grasp that the invention of PTL 3 is an IPS mode using a p-type liquid-crystal composition from the fact that the electric force lines and the long axis direction of the liquid-crystal molecules are identical.

However, since the IPS mode as shown in PTL 3 does not produce a complete parallel electric field, unlike the FFS mode, problems of a low opening ratio and transmittance occur. Furthermore, in the case of using a p-type material as shown in PTL 3, even if reduction of light transmittance by coloring the alignment film which is an object of the literature can be improved, the long axis of the liquid-crystal molecules close to the pixel electrode is inclined along the electric field of the edge to decrease transmittance, thus causing a new problem of reduction of transmittance.

An object of the present invention is to solve the above problems and to provide a liquid-crystal display element using an n-type liquid-crystal composition capable of realizing excellent display characteristics by being used in an FFS mode liquid-crystal display element, which is excellent in various characteristics as a liquid-crystal display element, such as dielectric anisotropy (Δ∈), viscosity (η), a nematic phase-isotropic liquid transition temperature (T_(NI)), nematic phase stability at low temperatures, and rotational viscosity (γ₁).

Solution to Problem

As a result of diligent studies to solve the above problems and examining various configurations of the liquid-crystal compositions optimal for an FFS mode liquid-crystal display element, the present inventors completed the present invention.

The present invention provides a liquid-crystal display element having a first substrate and second substrate disposed to face each other, a liquid-crystal layer containing a liquid-crystal composition with which a gap between the first substrate and the second substrate is filled, an electrode layer including a common electrode including a transparent conductive material, a plurality of gate bus lines and data bus lines disposed in a matrix shape, a thin film transistor provided at the intersection at which the gate bus lines and the data bus lines intersect, each other, and a pixel electrode including a transparent conductive material and forming a fringe electric field between the common electrode and the pixel electrode by being driven by the thin film transistor, for each pixel on the first substrate, and photo-alignment film layers inducing homogeneous alignment, which are formed between the liquid-crystal layer and the first substrate and between the liquid-crystal layer and the second substrate, respectively, in which a distance R between the pixel electrode and the common electrode is smaller than a distance G between the first substrate and the second substrate, and the liquid-crystal composition contains at least one compound selected from the group consisting of compounds represented by the following General Formula (I), which has negative dielectric anisotropy, a nematic phase-isotropic liquid transition temperature of equal to or higher than 60° C., and an absolute value of the dielectric anisotropy of equal to or greater than 2.

In the formula, each of R¹ and R² independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms. A represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group, k represents 1 or 2, and in a case where k is 2, two A's may be the same as or different from each other.

Advantageous Effects of Invention

The FFS mode liquid-crystal display element of the present invention has excellent high speed response, a feature in which generation of display defects is low, and excellent display characteristics. The liquid-crystal display element of the present invention is useful for a display element of a liquid-crystal TV, a monitor, or the like.

In the present invention, in a case where an n-type liquid-crystal composition is used, since the polarization direction of the n-type composition is in the short axis direction of the molecule, the influence by a fringe electric field only causes the liquid-crystal molecules to rotate along the long axis, the long axes of molecules maintain parallel arrangement, thereby reducing the decrease in transmittance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically showing one example of a configuration of a liquid-crystal display element of the present invention

FIG. 2 is an enlarged plan view of a region surrounded by a II line of an electrode layer 3 formed on a substrate 2 in FIG. 1

FIG. 3 is a sectional view obtained by cutting the liquids-crystal display element shown in FIG. 1 in a III-III line direction in FIG. 2

FIG. 4 is a view schematically showing an alignment direction of a liquid-crystal induced by an alignment film 4

FIG. 5 is an enlarged plan view of another example of the region surrounded by the II line of the electrode layer 3 formed on the substrate 2 in FIG. 1

FIG. 6 is a sectional view of another example obtained by cutting the liquid-crystal display element shown in FIG. 1 in the III-III line direction in FIG. 2.

DESCRIPTION OF EMBODIMENTS

As described above, the present invention is based on the finding of an n-type liquid-crystal composition optimal for an FFS mode liquid-crystal display element. A first embodiment of the present invention is a liquid-crystal display element having a first substrate and a second substrate disposed to face each other, a liquid-crystal layer containing a liquid-crystal composition with which a gap between the first substrate and the second substrate is filled, an electrode layer including a common electrode including a transparent conductive material, a plurality of gate bus lines and data bus lines disposed in a matrix shape, a thin film transistor provided at the intersection at which the gate bus lines and the data bus lines intersect each other, and a pixel electrode including a transparent conductive material and forming a fringe electric field between the common electrode and the pixel electrode driven by the thin film transistor, for each pixel on the first substrate, and photo-alignment film layers inducing homogeneous alignment, which are formed between the liquid-crystal, layer and the first substrate and between, the liquid-crystal layer and the second substrate, respectively, in which a distance R between the pixel electrode and the common electrode is smaller than a distance G between the first substrate and the second substrate, and the liquid-crystal composition contains at least one type of compound selected from the compound group represented by the following General Formula (I), which has negative dielectric anisotropy, a nematic phase-isotropic liquid transition temperature of equal to or higher than 60° C., and an absolute value of dielectric anisotropy of equal to or greater than 2.

In the formula, each of R¹ and R² independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 9 carbon atoms, A represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group, k represents 1 or 2, and in a case where k is 2, two A's may be the same as or different from each other.

In the present invention, by the alignment film being a photo-alignment film, it is possible to reduce the decrease in alignment properties with respect to the liquid-crystal molecules due to rubbing irregularity, and it is possible to provide an FFS mode liquid-crystal display element, having excellent transmittance characteristics.

A thin film transistor and a transparent electrode layer are formed on a substrate, and an alignment film is formed thereon. If performing alignment processing by a rubbing method which is a contact method, random scratches are formed on the surface of the alignment film by rubbing. In particular, in the first substrate on which a thin film transistor or a transparent electrode layer pattern has been formed, deeper scratches due to steps due to the thin film transistor or the transparent electrode layer pattern and the diameter (several tens of μm) of the fiber of buff cloth of the rubbing roller are likely to be formed along the steps. Since, at the areas where the scratches have been formed the liquid-crystal molecules can not be arrayed in a certain direction at the time of electric field off, light leakage occurs in the liquid-crystal panel at the time of displaying black. As a result, a contrast of equal to or greater than a certain value is less likely to be obtained.

Furthermore, in the resolution mode called 4K recently put into practical use, with the calculation example of a 40-inch panel, 1 pixel size becomes 0.23 mm. In addition, in the resolution mode called 8K recently put into practical use, with the calculation example of a 40-inch panel, 1 pixel size is fine to the extent of 0.11 mm. That is, since 1 pixel size is close to the diameter of a fiber of a buff cloth of the rubbing roller, there is a concern that, by the scratches formed at the time of being subjected to alignment processing by a rubbing method, in a pixel unit or an intermittent pixel array unit, the areas where the liquid-crystal molecules can not be arrayed in a certain direction at the time of electric field off are generated, and a significant decrease in contrast due to a large amount of light leakage at the time of displaying black or a large number of display defects are caused.

Since scratches are not generated on the surface of the alignment film in performing alignment processing in a non-contact fey a photo-alignment method, it is possible to achieve a clear black display in which there is no light leakage and the contrast is high.

Therefore, as the configuration elements of the liquid-crystal display element according to the present invention, a pair of substrates, an electrode layer, a liquid-crystal layer, and a photo-alignment film layer are essential elements. In addition, the liquid-crystal composition according to the present invention constituting a liquid-crystal layer includes one or more of compounds selected from the compound group represented by General Formula (I). In addition, as described below, the liquid-crystal composition of the present invention preferably further includes at least one compound selected from the group consisting of the compounds represented by each of General Formulas (II) and (IV). Hereinafter, respective configuration elements will be described in detail.

(Liquid-Crystal Layer)

One embodiment of the liquid-crystal composition of the present invention will be described below. The liquid-crystal composition of the present invention is preferably applied to an FFS mode liquid-crystal display element. In addition, the liquid-crystal layer according to the present invention is a layer including a liquid-crystal composition, and the average thickness of the liquid-crystal layer is preferably 2 to 10 μm, and more preferably 2.5 to 6.0 μm.

As described above, the liquid-crystal composition of the present invention necessarily includes the compound represented by General Formula (I). As a first component, one type or two or more types of compounds represented by General Formula (I) may be contained. In addition, as described below, the liquid-crystal composition of the present invention may further contain at least one type of compound selected from the group consisting of the compounds represented by General Formula (II) and the compounds represented by General Formula (IV).

In General Formula (I), each of R¹ and R² independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, A represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group, k represents 1 or 2, and in a case where k is 2, two A's may be the same as or different from each other.

The lower limit value of the total content of the compound represented by General Formula (I) is preferably 5% by mass, more preferably 10% by mass, still more preferably 15% by mass, particularly preferably 20% by mass, and most preferably 25% by mass, and the upper limit value thereof is preferably 65% by mass, more preferably 55% by mass, still more preferably 50% by mass, particularly preferably 47% by mass, and moat preferably 45% by mass, with respect to the content of the entirety of compositions.

Specific examples of the compounds represented by General Formula (I) include compounds represented by the compound group represented by each of the following General Formulas (I-a) to (I-e).

In General Formulas (I-a) to (I-e), each of R¹¹ to R¹⁵ and R²¹ to R²⁵ independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms.

In a case where the compounds selected from the compound group represented by each of General Formulas (I-a) to (I-e) are contained, one to ten types thereof are preferably contained, one to eight types thereof are particularly preferably contained, one to five types thereof are particularly preferably contained, and two or more types thereof are also preferably contained.

Each of R¹¹ to R¹⁵ and R²¹ to R²⁵ independently represents preferably an alkyl group having 1 to 8 carbon atoms, en alkenyl group having 2 to 8 carbon atoms, or an alkoxy group having 2 to 8 carbon atoms, and more preferably an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkoxy group having 2 to 5 carbon atoms, and in the case of representing an alkenyl group, the structures represented by each of the following Formulas (i) to (iv) are preferable.

In the formulas, the right terminal is bonded to the ring structure.

R¹¹ and R²¹, R¹² and R²², R¹³ and R²³, R¹⁴ and R²⁴, and R¹⁵ and R²⁵ may be the same as or different from each other, but it is preferable to represent different substituents.

From these points of view, for example, as the compound represented by General Formula (I), at least one type of compound selected from the confound group represented by the following General Formula (III) is preferably contained.

In the formula, R⁵ represents a hydrogen atom or a methyl group, and R⁶ represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms.

As the compound represented by General Formula (III) according to the present invention, more specifically, the compounds described below are preferable.

In a case where the compound represented by General Formula (III) according to the present invention is contained, the lower limit value of the content of the compound represented by General Formula (III) in the liquid-crystal composition is preferably 5% by mass, more preferably 15% by mass, still more preferably 20% by mass, particularly preferably 23% by mass, and most preferably 25% by mass, and the upper limit value thereof is preferably 70% by mass, more preferably 60% by mass, still more preferably 55% by mass, particularly preferably 52% by mass, and most preferably 50% by mass. More specifically, in a case where the response speed is regarded as important, the lower limit value thereof is preferably 20% by mass, more preferably 30% by mass, still more preferably 35% by mass, particularly preferably 38% by mass, and most preferably 35% by mass, and the upper limit value thereof is preferably 70% by mass, more preferably 60% by mass, still more preferably 55% by mass, particularly preferably 52% by mass, and most preferably 50% by mass, and in a case where the driving voltage further is regarded as important, the lower limit value thereof is preferably 5% by mass, more preferably 15% by mass, still more preferably 20% by mass, particularly preferably 23% by mass, and most preferably 25% by mass, and the upper limit value thereof is preferably 60$ by mass, more preferably 50% by mass, still more preferably 45% by mass, particularly preferably 42% by mass, and most preferably 40% by mass. Regarding the proportion of the compound represented by General Formula (III), the lower limit value of the content of the compound represented by General Formula (III) is preferably 60% by mass, more preferably 70% by mass, still more preferably 75% by mass, particularly preferably 78% by mass, and most preferably 80% by mass, and the upper limit value thereof is preferably 90% by mass, more preferably 95% by mass, still more preferably 97% by mass, particularly preferably 99% by mass, and preferably 100% by mass, with respect to the total content of the compound represented by General Formula (I) in the liquid-crystal composition.

In addition, as the compounds represented by each of General Formulas (I-a) to (I-e) other than the compounds represented by General Formula (III), more specifically, the compounds described below are preferable.

Among these, the compounds represented by each of Formulas (III-a2), (III-b2), (I-a1) to (I-a6), (I-b2), (I-b6), (I-d1), (I-d2), (I-d), and (I-e2) are preferable.

The liquid-crystal composition of the present invention may further include the compound represented by General Formula (II). As a second component, one type or two or more types of compounds represented by General Formula (II) may be contained, and more preferably, the liquid-crystal composition of the present invention may further include at least one type of compound selected from the group consisting of the compounds represented by General Formula (II) and the compounds represented by General Formula (IV).

In General Formula (II), R³ represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, R⁴ represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms, B represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group, m represents 0, 1, or 2, and in a case where m is 2, two B's may be the same as or different from each other.

The lower limit value of the content of the compound represented by General Formula (II) in the liquid-crystal composition is preferably 10% by mass, more preferably 20% by mass, still more preferably 25% by mass, particularly preferably 28% by mass, and most preferably 30% by mass, and the upper limit value thereof is preferably 85% by mass, more preferably 75% by mass, still more preferably 70% by mass, particularly preferably 67% by mass, and most preferably 65% by mass.

As the compound represented by General Formula (II), at least one or more types are preferably selected, and two or more types are more preferably selected, from among the compound group represented by each of the following General Formulas (IIa) to (IIc).

In the formulas, each of R³¹ to R³³ has the same meaning as R³ in General Formula (II) and each of R⁴¹ to R⁴³ has the same meaning as R⁴ in General Formula (II).

Specifically, the compounds represented by General Formula (IIa) are preferably the compounds represented by each of the following Formulas (IIa-1) to (IIa-8).

The compounds represented by each of Formulas (IIa-1) to (IIa-4) are more preferable, and the compounds represented by Formula (IIa-1) or (IIa-3) are still more preferable.

The lower limit value of the compound represented by General Formula (IIa) is preferably 2% by mass and more preferably 3% by mass, and the upper limit value thereof is preferably 45% by mass, more preferably 35% by mass, still more preferably 30% by mass, particularly preferably 27% by mass, and most preferably 25% by mass.

In a case where four or more types of compounds represented by General Formula (IIa) are used, the compounds represented by each of Formulas (IIa-1) to (IIa-4) are preferably used in combination, and the content of the compounds represented by each of Formulas (IIa-1) to (IIa-4) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, and still more preferably equal to or greater than 80% by mass, with respect to the compounds represented by General Formula (IIa).

In a case where three types of compounds represented by General Formula (IIa) are used, the compounds represented by Formula (IIa-1), (IIa-2), or (IIa-3) are preferably used in combination, and the content of the compounds represented by Formula (IIa-1), (IIa-2), or (IIa-3) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IIa).

In a case where two types of compounds represented by General Formula (IIa) are used, the compounds represented by Formula (IIa-1) or (IIa-3) are preferably used in combination, and the content of the compounds represented by Formula (IIa-1) or (IIa-3) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IIa).

Specifically, the compounds represented by General Formula (IIb) are preferably the compounds represented by each of the following Formulas (IIb-1) to (IIb-6).

The compounds represented by each of Formulas (IIb-1) to (IIb-4) are more preferable, the compounds represented by each of Formulas (IIb-1) to (IIb-3) are still more preferable, and the compounds represented by Formula (IIb-1) or (IIb-3) are particularly preferable.

In a case where four or more types of compounds represented by General Formula (IIb) are used, the compounds represented by each of Formulas (IIb-1) to (IIb-4) are preferably used in combination, and the content of the compounds represented by each of Formulas (IIb-1) to (IIb-4) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IIb).

In a case where three types of compounds represented by General Formula (IIb) are used, the compounds represented by each of Formulas (IIb-1) to (IIb-3) are preferably used in combination, and the content of the compounds represented by each of Formulas (IIb-1) to (IIb-3) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IIb).

In a case where two types of compounds represented by General Formula (IIb) are used, the compounds represented by Formula (IIb-1) or (IIb-3) are preferably used in combination, and the content of the compounds represented by Formula (IIb-1) or (IIb-3) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IIb).

Specifically, the compounds represented by General Formula (IIc) are preferably the compounds represented by each of the following Formulas (IIc-1) to (IIc-4).

Furthermore, the compounds represented by Formula (IIc-1) or (IIc-2) are preferable.

In a case where two or more types of compounds represented by General Formula (IIc) are used, the compounds represented by Formula (IIc-1) or (IIc-2) are preferably used in combination, and the content, of the compounds represented by Formula (IIc-1) or (IIc-2) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IIc).

The liquid-crystal composition of the present invention may further include the compound represented by General Formula (IV). As a third component, one type or two or more types of compounds represented by General Formula (IV) may be contained, and more preferably, the liquids-crystal composition of the present invention may further include at least one type of compound selected from the group consisting of the compounds represented by General Formula (II) and the compounds represented by General Formula (IV). Here, the compound represented by General Formula (II) is not included in the compound represented by General Formula (IV).

In the formula, each of and R⁷ and R⁸ independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, one or more hydrogen atoms in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with a fluorine atom, any methylene group in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with an oxygen atom as long as the oxygen atom is not continuously bonded to another oxygen atom or may be substituted, with a carbonyl group as long as the carbonyl group is not continuously bonded to another carbonyl group, each of A¹ and A² independently represents a 1,4-cyclohexylene group, a 1,4-phenylene group, or a tetrahydropyran-2,5-diyl group, in a case where A¹ or/and A² represent a 1,4-phenylene group, one or more hydrogen atoms in the 1,4-phenylene group may be substituted with a fluorine atom, each of Z¹ and Z² independently represents a single bond, —OCH₂—, —OCF₂—, —CH₂O—, or CF₂O—, each of n¹ and n² independently represents 0, 1, 2, or 3, n¹+n² is 1 to 3, and in a case where a plurality of A¹'s, A²'s, Z¹'s, and/or Z²'s are present, these may be the same as or different from each other, with the proviso that a compound in which n¹ is 1 or 2, n² is 0, at least one of A¹ 's is a 1,4-cyclohexylene group, and all Z¹'s are single bonds is excluded.

The lower limit value of the content of the compound represented by General Formula (IV) in the liquid-crystal composition is preferably 2% by mass, more preferably 3% by mass, still more preferably 4% by mass, and particularly preferably 5% by mass, and the upper limit value thereof is preferably 45% by mass, more preferably 35% by mass, still more preferably 30% by mass, particularly preferably 27% by mass, and most preferably 25% by mass.

In General Formula (IV), when the bonding ring structure is cyclohexane or tetrahydropyran, each of R⁷ and R⁸ is preferably an alkyl group or an alkenyl group, and when the bonding ring structure is benzene, each of R⁷ and R⁸ is preferably an alkyl group, an alkoxy group, or an alkenyl group. When the bonding ring structure is cyclohexane or tetrahydropyran, each of R⁷ and R⁸ preferably represents an alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 3 to 5 carbon atoms, and still more preferably represents an alkyl group having 3 or 5 carbon atoms, and is preferably linear. In addition, in General formula (IV), when the bonding ring structure is benzene, each of R⁷ and R⁸ preferably represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, preferably represents an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 3 to 5 carbon atoms or an alkoxy group having 2 to 4 carbon atoms, more preferably represents an alkyl group having 3 or 5 carbon atoms or an alkoxy group having 2 or 4 carbon atoms, and still more preferably represents an alkoxy group having 2 or 4 carbon atoms, and is preferably linear.

In the present invention, in a case where the improvement of response speed of the liquid-crystal display element, is regarded as important, an alkenyl group is preferable, and in a case where the reliability of a voltage holding ratio is regarded as important, an alkyl group is preferable. As the alkenyl group, the structures represented by each of the following Formulas (i) to (iv) are preferable.

In the formulas, the right terminal is bonded to the ring structure.

Each of A¹ and A² is independently preferably a 1,4-cyclohexylene group, a 1,4-phenylene group, or a tetrahydropyran-2,5-diyl group.

In a case where the reduction of viscosity is regarded as important, each of Z¹ and Z² is independently preferably a single bond, and in a case where the increase in the absolute value of Δ∈ is regarded as important, —OCH₂—, —OCF₂—, —CH₂O—, or —CF₂O— is preferable, and the oxygen atom is preferably disposed so as to be connected to 2,3-difluorobenzene-1,4-diyl group.

n¹+n² is preferably equal to or less than 2, and in a case where the reduction of viscosity is regarded as important, n¹+n² is preferably 1, and in a case where T_(Ni) is regarded as important or the increase in Δn is regarded as important, n¹+n² is preferably 2.

The compound represented by General Formula (IV) is preferably selected from the compound group represented by each of the following General Formulas (IVa1) and (IVa2).

In the formulas, each of R^(7a1), R^(7a2), R^(8a1), and R^(8a2) independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, one or more hydrogen atoms in the alkyl group, the alkenyl group, the alkoxy group, or alkenyloxy group may be substituted with a fluorine atom, any methylene group in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with an oxygen atom as long as the oxygen atom is not continuously bonded to another oxygen atom or may be substituted with a carbonyl group as long as the carbonyl group is not continuously bonded to another carbonyl group, n^(a2) represents 0 or 1, A^(1a2) represents a 1,4-cyclohexylene group, a 1,4-phenylene group, or a tetrahydropyran-2,5-diyl group, and one or more hydrogen atoms in the 1,4-phenylene group of General Formulas (IVa1) and (IVa2) may be substituted with a fluorine atom.

Specifically, the compounds represented by General Formula (IVa1) are preferably the compounds represented by each of the following Formulas (IVa1-1) to (IVa1-8).

The compounds represented by each of Formulas (IVa1-1) to (IVa1-4) are more preferable, the compounds represented by each of Formulas (IVa1-1) to (IVa1-3) are still more preferable, and the compounds represented by Formula (IVa1-1) are particularly preferable.

In a case where four or more types of compounds represented by General Formula (IVa1) are used, the compounds represented by each of Formulas (IVa1-1) to (IVa1-4) are preferably used in combination, and the content of the compounds represented by each of Formulas (IVa1-1) to (IVa1-4) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IVa1).

In a case where three types of compounds represented by General Formula (IVa1) are used, the compounds represented by each of Formulas (IVa1-1) to (IVa1-3) are preferably used in combination, and the content of the compounds represented by each of Formulas (IVa1-1) to (IVa1-3) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IVa1).

In a case where two types of compounds represented by General Formula (IVa1) are used, the compounds represented by Formula (IVa1-1) or (IVa1-3) are preferably used in combination, and the content of the compounds represented by Formula (IVa1-1) or (IVa1-3) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compounds represented by General Formula (IVa1).

Specifically, the compounds represented by General Formula (IVa2) are preferably the compounds represented by each of the following General Formulas (IVa2-1) to (IVa2-9).

In the formulas, R⁷ has the same meaning as R⁷ in General Formula (IV), and R⁸ has the same meaning as R⁸ in General Formula (IV).

In a case where the compound represented by General Formula (IVa2) is used, the compound represented by Formula (IVa2-1) is preferably used, and the content of the compound represented by Formula (IVa2-1) is preferably equal to or greater than 50% by mass, more preferably equal to or greater than 70% by mass, still more preferably equal to or greater than 80% by mass, particularly preferably equal to or greater than 85% by mass, and most preferably equal to or greater than 90% by mass, with respect to the compound represented by General Formula (IVa2).

In General formula (IVa2), each of R⁷ and R⁸ independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, preferably represents an alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, more preferably represents an alkyl group having 2 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, and still more preferably represents an alkyl group having 2 to 5 carbon atoms, and is preferably linear. In a case where both R⁷ and R⁸ are alkyl groups, the numbers of carbon atoms of the alkyl groups are preferably different.

In more detail, compounds in which R⁷ represents a propyl group and R⁸ represents an ethyl group, or compounds in which R⁷ represents a butyl group and R⁸ represents an ethyl group are preferable.

In the application, a 1,4-cyclohexyl group is preferably a trans-1,4-cyclohexyl group.

In a case where the liquid-crystal composition of the present invention include the compound represented by General Formula (I) or (II), the liquid-crystal composition can further contain the compound represented by General Formula (IV) (here, the compound represented by General Formula (II) is exclude). The total content of the compounds represented by General Formula (I), (II), or (IV) contained in the liquid-crystal composition is preferably 80% to 100% by mass, more preferably 85% to 100% by mass, still more preferably 90% to 100% by mass, particularly preferably 95% to 100% by mass, and most preferably 97% to 100% by mass,

The lower limit value of the total content of the compounds represented by General Formula (I) or (II) contained in the liquid-crystal composition of the present application is preferably 55% by mass, more preferably 65% by mass, still more preferably 70% by mass, particularly preferably 73% by mass, and most preferably 75% by mass, and the upper limit value thereof is preferably 85% by mass, more preferably 90% by mass, still more preferably 92% by mass, particularly preferably 94% by mass, and roost preferably 95% by mass.

In a case where the liquid-crystal composition of the present invention includes the confound represented by General Formula (I) or (IV), the liquid-crystal composition can further contain the compound represented by General Formula (II) (here, the compound represented by General Formula (IV) is exclude). The total content of the compounds represented by General Formula (I), (II), or (IV) contained in the liquid-crystal composition is preferably 80% to 100% by mass, more preferably 85% to 100% by mass, still more preferably 90% to 100% by mass, particularly preferably 95% to 100% by mass, and most preferably 97% to 100% by mass,

The lower limit value of the total content of the compounds represented by General Formula (I) or (IV) contained in the liquid-crystal composition of the present application is preferably 55% by mass, more preferably 65% by mass, still more preferably 70% by mass, particularly preferably 73% by mass, and most preferably 75% by mass, and the upper limit value thereof is preferably 85% by mass, more preferably 90% by mass, still more preferably 92% by mass, particularly preferably 94% by mass, and most preferably 95% by mass.

The liquid-crystal composition of the present invention preferably does not contain a compound having a structure in which oxygen atoms in the peracid (—CO—OO—) structure or the like in a molecule are banded to each other.

In a case where the reliability or the long-term stability of the liquid-crystal composition is regarded as important, the content of a compound having a carbonyl group is preferably equal to or less than 5% by mass, more preferably equal to or less than 8% by mass, and still more preferably equal to or less than 1% by mass, with respect to the total mass of the composition, and it is preferred that the compound having a carbonyl group is not contained substantially.

The content of a compound in which all the ring structures in the molecule are 6-membered rings is preferably increased, and the content of the compound in which all the ring structures in the molecule are 6-membered rings is preferably equal to or greater than 80% by mass, more preferably equal to or greater than 90% by mass, and still more preferably equal to or greater than 95% by mass, with respect to the total mass of the composition, and it is most preferable that the liquid-crystal composition is substantially constituted of only the compound in which all the ring structures in the molecule are 6-membered rings.

To suppress the deterioration due to oxidation of the liquid-crystal composition, the content of a compound having a cyclohexenylene group as a ring structure is preferably decreased, and the content of the compound having a cyclohexenylene group is preferably equal to or less than 10% by mass and more preferably equal to or less than 5% by mass with respect to the total mass of the composition, and it is still more preferred that the compound having a cyclohexenylene group is not contained substantially.

To suppress the deterioration due to oxidation of the liquid-crystal composition, the content of a compound having —CH═CH— as a connecting group is preferably decreased, and the content of the compound is preferably equal to or less than 10% by mass and more preferably equal to or less than 5% by mass with respect to the total mass of the composition, and it is still more preferred that the compound is not contained substantially.

In a case where the improvement of viscosity or T_(Ni) is regarded as important, the content of a compound having a 2-methylbenzene-1,4-diyl group in which a hydrogen atom may be substituted with halogen in the molecule is preferably decreased, and the content of the compound having a 2-methylbenzene-1,4-diyl group in the molecule is preferably equal to or less than 10% by mass and more preferably equal to or less than 5% by mass with respect to the total mass of the composition, and it is still wore preferred that the compound having a 2-methylbenzene-1,4-diyl group is not contained substantially.

In a case where the compound contained in the composition of the present invention has an alkenyl group as a side chain, and in a case where the alkenyl group is bonded to cyclohexane, the number of carbon atoms in the alkenyl group is preferably 2 to 5, and in a case where the alkenyl group is bonded to benzene, the number of carbon atoms in the alkenyl group is preferably 4 or 5, and it is preferable that the unsaturated bond of the alkenyl group and benzene are net directly bonded. In addition, in a case where the stability of the liquid-crystal composition is regarded as important, the content of a compound having an alkenyl group as a side chain and a 2,3-difluorobenzene-1,4-diyl group is preferably decreased, and the content of the compound is preferably equal to or less than 10% by mass and more preferably equal to or less than 5% by mass with respect to the total mass of the composition, and it is still more preferred that the compound is not contained substantially.

The value of the dielectric anisotropy Δ∈ of the liquid-crystal composition of the present invention is negative dielectric anisotropy, and the absolute value of the dielectric anisotropy is equal to or greater than 2. The value of the dielectric anisotropy Δ∈ at 25° C. is preferably −2.0 to −6.0, more preferably −2.5 to −5.0, and particularly preferably −2.5 to −4.0, and in more detail, in a case where the response speed is regarded as important, the value is preferably −2.5 to −3.4, and in a case where the driving voltage is regarded as important, the value is preferably −3.4 to −4.0.

In addition, in the liquid-crystal composition according to the present invention, the compound represented by General Formula (I) may be referred to as a nonpolar component, and the compounds represented by each of General Formulas (II) and (IV) may be referred to as a polar component.

In addition, a preferable composition of the liquid-crystal composition according to the present invention includes the compound represented by General Formula (I), and the compound represented by General Formula (II) and/or the compound represented by General Formula (IV).

The value of the refractive index anisotropy Δn at 25° C. of the liquid-crystal composition of the present invention is preferably 0.08 to 0.13, and more preferably 0.09 to 0.12. In more detail, in the case of corresponding to a thin cell gap, 0.10 to 0.12 is preferable, and in the case of corresponding to a thick, cell gap, 0.08 to 0.10 is preferable.

A rotational viscosity (γ₁) of the liquid-crystal composition of the present invention preferably is equal to or less than 150, more preferably equal to or less than 130, and particularly preferably equal to or less than 120.

In the liquid-crystal composition of the present invention, Z which is a function of the rotational viscosity and the refractive index anisotropy preferably shows specific values. Z=γ1/Δn ²  [Equation 1]

In the equation, γ₁ represents the rotational viscosity, and Δn represents the refractive index anisotropy.

Z is preferably equal to or less than 13,000, more preferably equal to or leas than 12,000, and particularly preferably equal to or less than 11,000.

The nematic phase-isotropic liquid phase transition temperature (T_(Ni)) of the liquid-crystal composition of the present invention is equal to or higher than 60° C., preferably equal to or higher than 75° C., more preferably equal to or higher than 80° C., and still more preferably equal to or higher than 90° C.

The liquid-crystal composition of the present invention is required to have specific resistance of equal to or greater than 10¹² (Ω·m), and preferably 10¹³ (Ω·m), and more preferably equal to or greater than 10¹⁴ (Ω·m).

The liquid-crystal composition of the present invention may contain typical nematic liquid-crystal, smectic liquid-crystal, cholestatic liquid-crystal, an antioxidant, an ultraviolet absorber, or the like other than the compounds described above according to the application, in a case where the chemical stability of the liquid-crystal composition is required, the compound preferably does not have a chlorine atom in the molecule thereof, and in a case where the stability of the liquid-crystal composition to light such as ultraviolet rays is required, the compound desirably does not have a condensed ring or the like in which the conjugation length is long and the absorption peaks are present in the ultraviolet region in the molecule thereof, represented by a naphthalene ring or the like.

(Alignment Layer)

The alignment layer according to the present invention is preferably a photo-alignment film including a photoresponsive polymer of which the chemical structure changes in response to light.

Therefore, in the liquid-crystal display element using an n-type material, it is necessary to arrange the liquid-crystal molecules perpendicular to the longitudinal direction of a strip shape electrode, and if rubbing is performed perpendicularly to the longitudinal direction of the electrode, rubbing irregularity is inevitably increased due to unevenness of the electrode, thereby significantly reducing an alignment restricting force with respect to the liquid-crystal molecules. The present invention can solve such a problem.

In general, there are various types in the photo-alignment film, and examples thereof include a type utilizing photoisomerization to be caused by irradiating a compound having an azo group (for example, an azobenzene compound), a Schiff's base, an unsaturated bond portion such as a carbon-carbon double bond or the like with light, a type utilizing photodimerization of a cinnamic acid derivative or the like, and a type utilizing photofragmentation (photolysis) of a σ bond of Coumarin, chalcone, or the polymer itself (for example, photodecomposable polyimide or the like).

In more detail, the photoresponsive polymer is preferably at least one selected from the group consisting of a photoresponsive decomposition type polymer, a photoresponsive dimerization type polymer, and a photoresponsive isomerization type polymer, and a photoresponsive decomposition type polymer is particularly preferable.

As the photoresponsive decomposition, type polymer according to the present invention, it is preferable to utilize photofragmentation (photolysis) of a σ bond of the polymer itself. In more detail, in any case, the photoresponsive decomposition type polymer according to the present invention preferably has polysiloxane, polyimide, or a polyamic acid derivative structure as a main chain, and more preferably has polyimide or a polyamic acid derivative structure. The polyamic acid derivative is preferably an ester having an alkyl group having 1 to 5 carbon atoms or a salt of an alkyl ammonium having 1 to 18 carbon atoms.

The photoresponsive decomposition type polymer according to the present invention preferably contains at least one type of polymer selected from the group consisting of polyamic acid and polyimide obtained by reacting tetracarboxylic dianhydride and a diamine compound.

Examples of the tetracarboxylic dianhydride which is a raw material of polyimide and a polyamic acid derivative include the following.

In the formulas, each of Z¹, Z², Z³, and Z⁴ independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a chlorine atom, a fluorine atom, —NR₂, —SR, —OH, —CH₂COOR, —CH₂CH₂COOR, —COR, —NO₂, or —CN, and, here, at least one of Z¹, Z², Z³, and Z⁴ is not a hydrogen atom or a methyl group. R represents an alkyl group having 1 to 5 carbon atoms, and T represents a single bond, —CH₂—, —O—, —S—, —C(CH₃)₂—, —C(CF₃)₂—, —CO—, or —SO—.

T in the above formulas represents a single bond, —CH₂—, —O—, —S—, —C(CH₃)₂—, —C(CF₃)₂—, —CO—, or —SO—. Among the above compounds, Formula (TCA-1), (TCA-2), (TCA-3), (TCA-4), (TCA-5), (TCA-8), or (TCA-10) is preferable, and Formula (TCA-1) or (TCA-8) is particularly preferable.

Examples of the diamine compound which is a raw material of polyimide and a polyamic acid derivative include the following.

Among the above compounds. Formula (DA-1), (DA-25), (DA-31), (DA-32), or (DA-49) is preferable, and Formula (DA-1), (DA-25), or (DA-49) is particularly preferable.

In addition, in the photo-alignment film according to the present invention, in a case where a type utilizing photoisomerization is adopted, at least one of a tetracarboxylic anhydride and the diamine compound preferably includes at least one selected from the group consisting of the following Formula (TCA-38) and Formulas (DA-50) to (DA-56).

For example, in addition to (or in place of) the compounds of Formulas (TCA-1) to (TCA-37) exemplified as the tetracarboxylic anhydride, the compound represented by the following Formula (TCA-38) is preferably used.

For example, in addition to (or in place of) the compounds of Formulas (DA-1) to (DA-49), the use of the compound represented by each of the following Formulas (DA-50) to (DA-56) as the diamine compound:

is preferred.

In addition, in the photo-alignment film according to the present invention, in a case where a type utilizing photodimerization is adopted, at least one of the hydrogen atoms in a diamine compound represented by each of Formulas (DA-1) to (DA-49) is preferably has the following Formula (V), and more preferably includes at least one selected from the group consisting of Formulas (DA-50) to (DA-53).

That is, in addition to (or in place of) the compounds of Formulas (DA-1) to (DA-49), as the diamine compound, a compound obtained toy substituting the hydrogen atom in each of compounds of Formulas (DA-1) to (DA-49) with General Formula (V) is preferably used.

In the formula, the broken line represents a bond to the atom to which the hydrogen atom of (DA-1) to (DA-49) is bonded, each of G¹, G², G³, G⁴, and G⁵ independently represents a single bond, an alkylene group having 2 to 12 carbon atoms (one —CH₂— group or two or more non-adjacent —CH₂— groups may be substituted with —O—, —CO—, —COO—, —OCO—, —NR—, —NRCO—, —CONR—, —NRCOO—, —OCONR—, —NRCONR—, —CH═CH—, —CC—, or —OCOO—. R represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms), —OCH₂—, —CH₂O—, —COO—, —OCO—, —CH═CH—, —CF═CF—, —CF₂O—, —OCF₂—, —CF₂CF₂—, —CC—, —CH═CHCCO—, or —OCOCH═CH—. Here, any one or more of G¹, G², G³, G⁴, and G⁵ represent —CH═CHCOO— or —OCOCH═CH—. Each of n⁵, n⁶, n⁷, and n⁸ represents 0 or 1, each of E¹, E², E³, E⁴, and E⁵ independently represents trans-1,4-cyclohexylene, trans-1,4-dioxane-2,5-diyl, 1,4-naphthylene, 2,6-naphthylene, a pyridine-2,5-diyl group, a pyrimidine-2,5-diyl group, a 2,5-thiophenylene group, a 2,5-furanylene group, or a 1,4-phenylene group, these may be unsubstituted or one or more hydrogen atoms therein may be substituted with a fluorine atom, a chlorine atom, a methyl group, or a methoxy group, and Z represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 12 carbon atoms (one —CH₂— group or two or more non-adjacent —CH₂— groups may be substituted with —O—, —CO—, —COO—, —OCO—, —NR—, —NRCO—, —CONR—, —NRCOO—, —OCONR—, —NRCONR—, —CH═CH—, —CC—, or —OCOO—. R represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms), a cyano group, a nitro group, a hydroxyl group, or a carboxyl group.

Specific examples of the diamine compound include the following Formulas (DA-60) to (DA-63).

For the photodecomposition type photo-alignment film according to the present invention, from the viewpoint of being capable of exhibiting good liquid-crystal alignment properties, the tetracarboxylic anhydride is more preferably Formula (TCA-1), (TCA-2), (TCA-3), (TCA-4), (TCA-5), (TCA-33) (in Formula (TCA-33), T is particularly preferably —CO—), or TCA-34 (in Formula (TCA-34), T is preferably —CO—), and particularly preferably Formula (TCA-1), (TCA-2), (TCA-3), (TCA-4), or (TCA-5). In addition, for the photodecomposition type photo-alignment film according to the present invention, from the viewpoint of being capable of exhibiting good liquid-crystal alignment properties, the diamine compound is particularly preferably Formula (DA-1), (DA-25), or (DA-49).

Each of the tetracarboxylic anhydride and the diamine compound exemplified above may be used singly or in combination of two or more types thereof depending on required characteristics.

With respect to a preferable polyamic acid of the photoresponsive decomposition type polymer according to the present invention, as the mixing proportion between the tetracarboxylic dianhydride described above and the diamine compound described above, a proportion at which the acid anhydride group of the tetracarboxylic dianhydride becomes 0.2 to 2 equivalents is preferable and a proportion at which the acid anhydride group of the tetracarboxylic dianhydride becomes 0.3 to 1.2 equivalents is more preferable, with respect to one equivalent of the amino group of the diamine.

In addition, in the photo-alignment film according to the present invention, the synthesis reaction of polyamic acid by condensation of tetracarboxylic anhydride and a diamine compound is preferably performed in an organic solvent. The reaction temperature is preferably −20° C. to 150° C., and more preferably 0° C. to 100° C. In addition, the reaction time is preferably 0.1 to 24 hours, and more preferably 0.5 to 12 hours.

Examples of the organic solvent include an alcohol, a ketone, an ester, an ether, an aprotic polar solvent, a phenol and a phenol-derivative-based solvent, a halogenated hydrocarbon-based solvent, and a hydrocarbon-based solvent.

As the alcohol, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, or ethylene glycol monomethyl ether is preferable.

As the ketone, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone is preferable.

Examples of the ester include ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate, and diethyl malonate.

Examples of the ether include diethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, ethylene glycol-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and tetrahydrofuran.

As specific examples of the aprotic polar solvent, for example, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethylurea, or hexamethylphosphortriamide is preferable.

As the phenol and a derivative thereof, for example, m-cresol, xylenol, or halogenated phenol is preferable.

Examples of the halogenated hydrocarbon-based solvent include dichloromethane, 1,2-dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene, and o-dichlorobenzene.

Examples of the hydrocarbon-based solvent include hexane, heptane, octane, benzene, toluene, xylene, isoamylpropionate, isoamylisoburyrate, and diisopentyl ether.

The total amount of tetracarboxylic dianhydride and diamine compound with respect to the organic solvent is preferably 0.1% to 50% by weight with respect to the total amount of the reaction solution.

If tetracarboxylic dianhydride and a diamine compound are reacted in the conditions described above, a reaction solution including polyamic acid is obtained, the obtained reaction solution as it is may be supplied for preparation of an alignment film, after the polyamic acid included in the reaction solution is isolated, the polyamic acid may be supplied for preparation of an alignment film, or after the isolated polyamic acid is purified, the purified polyamic acid may be supplied for preparation of an alignment film.

In addition, in a case where polyimide is obtained by dehydrating and ring-closing the polyamic acid obtained above, the above-described reaction solution as it is may be subjected to a dehydration and ring-closing reaction, after the polyamic acid included in the reaction solution is isolated, the polyamic acid may be subjected to a dehydration and ring-closing reaction, or after the isolated polyamic acid is purified, the purified polyamic acid may be subjected to a dehydration and ring-closing reaction. Isolation and purification of the polyamic acid can be performed according to known methods.

As a method of obtaining polyimide by imidizing the polyamic acid obtained by the above reaction, polyimide can be obtained by imidization by dehydrating and ring-closing polyamic acid. Specifically, the imidization is performed by a method of heating the polyamic acid or a method of dissolving the polyamic acid in an organic solvent, adding a dehydrating agent and a dehydration and ring-closing catalyst to the solution, and heating if necessary.

As the organic solvent used in the dehydration and ring-closing reaction, organic solvents exemplified as those used in synthesis of polyamic acid can be exemplified, and thus, the description thereof will, not be repeated here.

Polyimide as the alignment film according to the present invention may be a completely imidized product obtained by dehydrating and ring-closing all the amic acid structures of the polyamic acid which is a precursor of the polyimide, or may be a partially imidized product in which an amic acid structure and an imide ring structure coexist obtained by dehydrating and ring-closing only a part of the amic acid structures. The imidization ratio of the polyimide according to the present invention is preferably equal to or greater than 30%, more preferably 40% to 99%, and still more preferably 45% to 98%. The imidization ratio indicates a proportion of the number of imide ring structures with respect to the total of the number of amic acid structures and the number of imide ring structures of the polyimide, as a percentage. Here, a part of the imide rings may be isoimide rings.

Moreover, in the present invention, in the measurement method of the Imidization ratio of polyimide, the proton derived from the structure which does not change before and after the imidization is determined as a reference proton, and by using the peak integration value of the proton and the proton peak integration value derived from the NH group of amic acid appearing in the vicinity of 9.5 to 10.0 ppm, the imidization ratio is calculated.

In the present invention, the temperature in a case where polyamic acid is thermally imidized in a solution is preferably 100° C. to 400° C., and more preferably 120° C. to 250° C. In this case, a method of performing the imidization while removing the water generated by the imidization reaction from the system is preferable.

In the present invention, in a case where polyamic acid is imidized by a catalyst, polyimide is obtained by adding a basic catalyst and an acid anhydride to the solution of polyamic acid obtained above, followed by stirring preferably at −20° C. to 250° C., and more preferably at 0° C. to 180° C. In addition, in this case, the amount of basic catalyst is 0.5 to 30 mol times the amount of amide acid group, and preferably 2 to 20 mol times, and the amount of acid anhydride is 1 to 50 mol times the amount of amido acid group, and preferably 3 to 30 mol times.

Examples of the basic catalyst include pyridine, collidine, lutidine, triethylamine, trimethylamine, tributylamine, and trioctylamine. In addition, examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride.

Moreover, the imidization ratio by catalyst imidization can be controlled by adjusting the amount of catalyst, the reaction temperature, and the reaction time.

In the present invention, in a case where the generated polyamic acid or polyimide is recovered from the reaction solution of polyamic acid or polyimide, precipitation may be performed by putting the reaction solution into a poor solvent. Examples of the poor solvent used in precipitation include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, and water. After the polymer precipitated by putting into the poor solvent is recovered by filtration, the polymer can be dried at ordinary temperature or by heating under ordinary pressure or reduced pressure.

With respect to a solution having a concentration of the polyamic acid and the polyimide according to the present invention of 10% by weight, the solution preferably has a viscosity of 10 to 800 mPa·s, and more preferably has a viscosity of 15 to 500 mPa·s. Moreover, the solution viscosity of the polymer (mPa·s) is a value measured with respect to a polymer solution having a concentration of 10% by weight prepared by using a good solvent (for example, γ-butyrolactone or N-methyl-2-pyrrolidone) relative to the polymer at 25° C. by using an E-type rotational viscometer.

As the photoresponsive decomposition type polymer according to the present invention, the photoresponsive dimerization type polymer represented by the following General Formula (1A) or (1B) other than the above-described formulas, a hydrolyzate thereof, or a condensate of the hydrolyzate is preferable.

In General Formula (1), Sp is a single bond or at least one type of divalent connecting group selected from the group consisting of —(CH₂)_(u)— (in the formula, u represents 1 to 20), —OCH₂—, —CH₂O—, —COO—, —OCO—, —CH═CH—, —CF═CF—, —CF₂O—, —OCF₂—, —CF₂CF₂—, and —C≡C—, one or more non-adjacent CH₂ groups in these substituents can be independently substituted with —O—, —CO—, —CO—O—, —O—CO—, —Si(CH₃)₂—O—Si(CH₃)₂—, —NR—, —NR—CO—, —CO—NR—, —NR—CO—O—, —O—CO—NR—, —NR—CO—NR—, —CH═CH—, —C≡C—, or —O—CO—O— (in the formulas, R independently represents hydrogen or an alkyl group having 1 to 5 carbon atoms), each of A¹ and A² independently represents a group selected from the group consisting of:

-   (a) a trans-1,4-cyclohexylene group (one methylene group or two or     more non-adjacent methylene groups present in the group may be     substituted with —O—, —NH—, or —S—), -   (b) a 1,4-phenylene group (one or two or more —CH═ present in the     group may be substituted with —N═) and -   (c) a 1,4-cyclohexenylene group, a 2,5-thiophenylene group, a     2,5-furanylene group, a 1,4-bicyclo(2.2.2) octylene group, a     naphthalene-1,4-diyl group, a naphthalene-2, 6-diyl group, a     decahydronaphthalene-2, 6-diyl group, and a     1,2,3,4-tetrahydronaphthalene-2, 6-diyl group,     each of the above-described groups (a), (b), and (c) may be     unsubstituted or one or more hydrogen atoms therein may be     substituted with a fluorine atom, a chlorine atom, a cyano group, a     methyl groups, or a methoxy group,

each of Z¹, Z², and Z³ independently represents a single bond, —(CH₂)_(u)— (in the formula, u represents 1 to 20), —OCH₂—, —CH₂O—, —COO—, —OCO—, —CH═CH—, —CF═CF—, —CF₂O—, —OCF₂—, —CF₂CF₂—, or —C≡C—, one or more non-adjacent CH₂ groups in these substituents can be independently substituted with —O—, —CO—, —CO—O—, —O—CO—, —Si(CH₃)₂—O—Si(CH₃)₂—, —NR—, —NR—CO—, —CO—NR—, —NR—CO—O—, —O—CO—NR—, —NR—CO—NR—, —CH═CH—, —C≡C—, or —O—CO—O— (in the formulas, R independently represents hydrogen or an alkyl group having 1 to 5 carbon atoms),

X is —O—, a single bond, —NR—, or a phenylene group,

R^(b) is a polymeric group, an alkoxy group, a cyano group, or a fluorinated alkyl group having 1 to 12 carbon atoms,

m is 0, 1, or 2, and

each of M_(b) and M_(d) may be the same as or different from each other, and Independently represents any one type of the monomer units of the following General Formula (U-1) to (U-13).

In General Formulas (U-1) to (U-10), the broken line represents a bond to Sp, R³ independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a halogen atom, an arbitrary hydrogen atom in each structure may be substituted with a fluorine atom, a chlorine atom, a methyl group, a phenyl group, or a methoxy group, in General Formulas (U-11) to (U-13), the broken line represents a bond to Sp, R¹ represents a tetravalent ring structure, R² represents a trivalent organic group, and R³ represents a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 15 carbon atoms, or an alkoxy group having 1 to 15 carbon atoms.

Each of y and w represents the molar fraction of a copolymer, y is greater than 0 and equal to or less than 1, w is equal to or greater than 0 and less than 1, n represents 4 to 100,000, and each of monomer units of M_(b) and M_(d) may be independently formed of one type of unit or two or more types of different units.

In addition, as a preferable aspect of the photoresponsive polymer represented by General Formula (1) according to the present invention, a photoresponsive dimerization type polymer in which Z² is a single bond is preferable.

Another photoresponsive dimerization type polymer according to the present invention is preferably a photoresponsive dimerization type polymer represented by the following General Formula (2).

In General Formula (2), each of M¹ and M² is independently at least one type of repeating unit selected from the group consisting of acrylate, methacrylate, 2-chloroacrylate, 2-phenylacrylate, acrylamide which may be N-substituted with a lower alkyl group, methacrylamide, 2-chloroacrylamide, 2-phenylacrylamid, vinyl ethers, vinyl esters, styrene derivatives, and siloxanes, M³ is independently at least one type of repeating unit selected from the group consisting of acrylate, methacrylate, 2-chloroacrylate, 2-phenylacrylate, acrylamide which may be N-substituted with lower alkyl, methacrylamide, 2-chloroacrylamide, 2-phenylacrylamide, vinyl ethers, vinyl esters, linear or branched alkyl esters of acrylic acid or methacrylic acid, alkyl esters of acrylic acid or methacrylic acid, alkyl vinyl ethers or alkyl vinyl esters, phenoxyalkyl acrylates, phenoxyalkyl methacrylates, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, phenylalkyl acrylates, phenylalkyl methacrylates, acrylonitrile, methacrylonitrile, styrene, 4-methyl styrene, and siloxanes,

each of A¹, B¹, C¹, A², B², and C² independently represents a group selected from the group consisting of:

-   (a) a trans-1,4-cyclohexylene group (one methylene group or two or     more non-adjacent methylene groups present in the group may be     substituted with —O—, —NH—, or —S—), -   (b) a 1,4-phenylene group (one or two or more —CH═'s present in the     group may be substituted with —N═), and -   (c) a 1,4-cyclohexenylene group, a 2,5-thiophenylene group, a     2,5-furanylene group, a 1,4-bicyclo(2.2.2) octylene group, a     naphthalene-1,4-diyl group, a naphthalene-2,6-diyl group, a     decahydronaphthalene-2,6-diyl group, and a     1,2,3,4-tetrahydronaphthalene-2,6-diyl group,

each of the above-described groups (a), (b), and (c) may be unsubstituted or one or more hydrogen atoms therein may be substituted with a fluorine atom, a chlorine atom, a cyano group, a methyl group, or a methoxy group,

each of S¹ and S² is independently a linear or branched alkylene group (—(CH₂)_(r)—) or —(CH₂)_(r)-L-(CH₂)_(s)— which has been substituted with one or more fluorine atoms, chlorine atoms, or cyano groups (in the formula, L means a single bond or —O—, —COO—, —OOC—, —NR¹—, —NR¹—CO—, —CO—NR¹—, —NR¹—COO—, —OCO—NR¹—, —NR¹—CO—NR¹—, —CH═CH—, or —C≡C—, in this case, R¹ means a hydrogen atom or a lower alkyl group, and each of r and s is an integer of 1 to 20 under the conditions of r+s≤24),

each of D¹ and D² independently includes —O—, —NR²—, or a group selected from the group consisting of the following (d) to (f):

(d) a trans-1,4-cyclohexylene group (one methylene group or two or more non-adjacent methylene groups present in the group may be substituted with —O—, —NH—, or —S—,

(e) a 1,4-phenylene group (one or two or more —CH═'s present in the group may be substituted with —N═), and

(f) a 1,4-cyclohexenylene group, a 2,5-thiophenylene group, a 2,5-furanylene group, a 1,4-bicyclo(2.2.2) octylene group, a naphthalene-1,4-diyl group, a naphthalene-2,3-diyl group, a decahydronaphthalene-2,6-diyl group, and a 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, it is meant that each of the above-described groups (d), (e), and (f) may be unsubstituted or one or more hydrogen atoms therein may be substituted with a fluorine atom, a chlorine atom, a cyano group, a methyl group, or a methoxy group, and at this time, R² is a hydrogen atom or a lower alkyl group,

each of X¹, X², Y¹, and Y² independently means a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group, a CH₂ group which may be substituted with a fluorine atom in some cases, or an alkyl group having 1 to 12 carbon atoms in which a plurality of non-adjacent CH₃ groups may be replaced by —O—, —COO—, —OOC—, and/or —CH═CH— in some cases,

each of Z^(1a), Z^(1b), Z^(2a), and Z^(2b) independently means a single bond, —(CH₂)t-, —O—, —CO—, —CO—O—, —O—OC—, —NR⁴—, —CO—NR⁴—, —NR⁴—CO—, —(CH₂)_(u)—O—, —O—(CH₂)_(u)—, —(CH₂)_(u)—NR⁴—, or —NR⁴—(CH₂), and at this time, R⁴ means a hydrogen atom or a lower alkyl group; t means an integer of 1 to 4; and u is an integer of 1 to 3,

each of p¹, p², q¹, and q² is independently 0 or 1,

each of R^(1a) and R^(2a) independently means a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, or a linear or branched alkyl group having 1 to 20 carbon atoms, an alkoxy group, an alkyl-COO—, alkyl-CO—NR³, or an alkyl-OCO group, at this time, R³ means a hydrogen atom or a lower alkyl group, one or more hydrogen atoms in the alkyl group or the alkoxy group may be substituted with a fluorine atom, a chlorine atom, a cyano group, or a nitro group, a CH₂ group or a plurality of non-adjacent CH₂ groups in the alkyl group or the alkoxy group may be substituted with —O—, —CH═CH—, or —C≡C—, and

each of n¹, n², and n³ is a comonomer molar fraction of 0<n¹≤1, 0≤n²<1, and 0≤n³≤0.5, respectively.

(Substrate, Electrode Layer)

A pair of substrates and an electrode layer which are configuration elements of the liquid-crystal display element according to the present invention will be described below, and for convenience, the configuration elements will be described in detail together with the description of the liquid-crystal display element according to the present invention. Hereinafter, one embodiment of the liquid-crystal display element according to the present invention will be described with, reference to drawings.

FIG. 1 is a view schematically showing a configuration of a liquid-crystal display element. In FIG. 1, for explanation, respective configuration elements are described in separated state for convenience. As described in FIG. 1, the liquid-crystal display element 10 according to the present invention is an FFS mode liquid-crystal display element having a liquid-crystal composition (or a liquid-crystal layer 5) sandwiched between a first transparent insulating substrate 2 and a second transparent insulating substrate 1 which are disposed to face each other, and has a feature of using the liquid-crystal composition of the present invention as the liquid-crystal composition. In the first transparent insulating substrate 2, an electrode layer 3 is formed on the surface of the liquid-crystal layer 5 side. In addition, the liquid-crystal display element 10 has a pair of photo-alignment films 4 inducing homogeneous alignment in direct contact with the liquid-crystal composition constituting the liquid-crystal layer 5 between the liquid-crystal layer 3 and the first transparent insulating substrate 2 and between the liquid-crystal layer 5 and the second transparent insulating substrate 8, respectively, and the liquid-crystal molecules in the liquid-crystal composition are aligned so as to be substantially parallel to the substrates 2 and 7 when no voltage is applied. As shown in FIGS. 1 and 3, the second substrate 7 and the first substrate 2 may be sandwiched between a pair of polarizing plates 1 and 8. In FIG. 1, a color filter 6 is provided between the second substrate 7 and an alignment film 4. Moreover, the form of the liquid-crystal display element according to the present invention may be a so-called color filter-on-array (COA), and a color filter may be provided between the electrode layer including a thin film transistor and the liquid-crystal layer, or a color filter may be provided between the electrode layer including the thin film transistor and the second substrate.

That is, the liquid-crystal display element 10 according to the present invention has a configuration in which the first polarizing plate 1, the first substrate 2, the electrode layer 3 including a thin film transistor, the alignment film 4, the liquid-crystal layer 5 including a liquid-crystal composition, the alignment film 4, the color filter 6, the second substrate 7, and the second polarizing plate 8 are sequentially stacked.

As the first substrate 2 and the second substrate 7, a transparent material having flexibility such as glass or plastic can be used, and one of substrates may be an opaque material such as silicons. The two substrates 2 and 7 are attached by a sealant or a sealing material such as an epoxy-based thermosetting composition disposed in the peripheral region, and to hold the distance between the substrates, for example, particle shape spacers such as glass particles, plastic particles, or alumina particles or spacer posts formed of a resin formed by photolithography may be disposed therebetween.

FIG. 2 is an enlarged plan view of a region surrounded by a II line of the electrode layer 3 formed on the substrate 2 in FIG. 1, FIG. 3 is a sectional view obtained by cutting the liquid-crystal display element shown in FIG. 1 in a III-III line direction in FIG. 2. As shown in FIG. 2, in the electrode layer 3 including a thin film transistor formed on the surface of the first substrate 2, a plurality of gate bus lines 25 for supplying a scanning signal and a plurality of data bus lines 25 for supplying a display signal are disposed in a matrix shape to intersect each other. Moreover, in FIG. 2, only a pair of gate bus lines 25 and a pair of data bus lines 24 are shown.

By the region surrounded by the plurality of gate bus lines 26 and the plurality of data bus lines 25, a unit pixel of the liquid-crystal display device is formed, and in the unit pixel, a pixel electrode 21 and a common electrode 22 are formed In the vicinity of the intersection at which the gate bus lines 26 and the data bus lines 25 intersect each other, a thin film transistor including a source electrode 27, a drain electrode 24, and a gate electrode 28 is provided. The thin film transistor is connected to the pixel electrode 21 as a switching element for supplying a display signal to the pixel electrode 21. In addition, a common line 29 is provided in parallel with the gate bus line 26. The common line 29 is connected to the common electrode 22 for supplying a common signal to the common electrode 22.

As shown in FIG. 3, one preferable aspect of the structure of the thin film transistor has, for example, a gate electrode 11 formed on the surface of the substrate 2, a gate insulating layer 12 provided so as to cover the gate electrode 11 and substantially cover the entire surface of the substrate 2, a semiconductor layer 13 formed on the surface of the gate insulating layer 12 so as to face the gate electrode 11, a protective film 14 provided so as to cover a part of the surface of the semiconductor layer 17, a drain electrode 16 provided so as to cover the end portion of one side of each of the protective layer 14 and the semiconductor layer 13 and come into contact with the gate insulating layer 12 formed on the surface of the substrate 2, a source electrode 17 provided so as to cover the end portion of the other side of each of the protective film 14 and the semiconductor layer 13 and come into contact with the gate insulating layer 12 formed on the surface of the substrate 2, and an insulation protecting layer 18 provided so as to cover the drain electrode 16 and the source electrode 17. An anodic oxide film (not shown) may be formed on the surface of the gate electrode 11 to eliminate steps with the gate electrode.

In the semiconductor layer 13, amorphous silicon, polycrystalline poly ail icon, or the like can be used, and it is also preferable to use a transparent semiconductor film such as a film of ZnO, IGZO (In—Ga—Zn—O), or ITO from the viewpoint of being capable of suppressing the adverse effect of the photocarrier due to light absorption and increasing the opening ratio of the element.

Furthermore, for the purpose of reducing the width or the height of the Schottky barrier, an ohmic contact layer 15 may be provided between the semiconductor layer 13 and the drain electrode 16 or the source electrode 17. In the ohmic contact layer, a material such as n-type amorphous silicon and n-type polycrystalline polysilicon, obtained by adding impurities such as phosphorus at a high concentration, can be used.

Each of the gate bus line 26, a data bus line 25, and the common line 22 is preferably a metal film, and more preferably Al, Cu, Au, Ag, Cr, Ta, Ti, Mo, W, Ni, or alloys thereof, and a case of using a wire of Al or an alloy thereof is particularly preferable. In addition, the insulation protecting layer 18 is a layer having an insulation function and formed of silicon nitride, silicon dioxide, a silicon oxynitride film, or the like.

In the embodiment shown in FIGS. 2 and 3, the common electrode 22 is a flat plate shape electrode formed on substantially the entire surface of the gate insulating layer 12, and on the other hand, the pixel electrode 21 is a comb shape electrode formed on the insulation protecting layer 18 covering the common electrode 22. That is, the common electrode 22 is disposed at a position closer to the first substrate 2 than the pixel electrode 21, and these electrodes are disposed to overlap each other through the insulation protecting layer IS. Each of the pixel electrode 21 and the common electrode 22 is formed of, for example, a transparent conductive material such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), or IZTO (Indium Zinc Tin Oxide). Since the pixel electrode 21 and the common electrode 22 are formed of transparent conductive materials, the area opened in a unit pixel area becomes large, and both the opening ratio and the transmittance are increased.

In addition, the pixel electrode 21 and the common electrode 22 are formed such that, the distance (also referred to as the minimum distance) R between the pixel electrode 21 and the common electrode 22 becomes smaller than the distance G between the first substrate 2 and the second substrate 7 to form a fringe electric field between these electrodes. Here, the distance R between electrodes represents a distance in the horizontal direction on the substrate between the electrodes. In FIG. 3, since the flat plate shape common electrode 22 and the comb shape pixel electrode 21 are overlapped, an example in which the minimum distance (or the distance between electrodes) R becomes 0 is shown, and since the minimum distance R becomes smaller than the distance (that is, a cell gap) G between the first substrate 2 and the second substrate 7, a fringe electric field E is formed. Therefore, in an FFS type liquid-crystal display element, it is possible to use a horizontal electric field formed in the vertical direction with respect to the line forming a comb shape of the pixel electrode 21 and a parabolic electric field. It is preferable that the electrode width l of the comb shape portion of the pixel electrode 21 and the gap width m of the comb shape portion of the pixel electrode 21 are formed in such an extent that all the liquid-crystal molecules in the liquid-crystal layer 5 can be driven by the electric field generated. In addition, the minimum distance R between the pixel electrode and the common electrode can be adjusted as the (average) film thickness of a gate insulating film 12.

The liquid-crystal display element according to the present invention is preferably a liquid-crystal display composition of the FFS mode using a fringe electric field, and if the shortest distance R between, the common electrode 22 and the pixel electrode 21 which are adjacent is shorter than the shortest distance G between the alignment layers 4 (the distance between substrates), a fringe electric field is formed between the common electrode and the pixel electrode, and it is possible to efficiently use the alignment of the horizontal direction and the vertical direction of the liquid-crystal molecules. In the case of an FFS mode liquid-crystal display element as a preferable aspect of the present invention, if a voltage is applied to the liquid-crystal molecules of which the long axis direction is disposed so as to be parallel to the alignment direction of the alignment layer, an equipotential line of the parabolic electric field between the pixel electrode 21 and the common electrode 22 is formed to the upper portion of the pixel electrode 21 and the common electrode 22, and the liquid-crystal molecules in the liquid-crystal layer 5 rotate in the liquid-crystal layer 5 along the formed electric field. In particular, since, as the liquid-crystal composition according to the present invention, liquid-crystal molecules having negative dielectric anisotropy are used, the long axis direction of the liquid-crystal molecules is rotated so as to be orthogonal to the electric field direction generated. The liquid-crystal molecules positioned near the pixel electrode 21 are likely to be influenced by a fringe electric field, but since in the liquid-crystal molecules having negative dielectric anisotropy, the polarization direction is in the short axis of the molecules, the long axis direction is not rotated in the direction orthogonal to the alignment layer 4, and the long axis direction of all liquid-crystal molecules in the liquid-crystal layer 5 is capable of maintaining the parallel direction with respect to the alignment film 4. Therefore, it is possible to obtain excellent transmittance characteristics compared to a liquid-crystal display element of the FFS mode in which the liquid-crystal molecules having positive dielectric anisotropy are used.

From the viewpoint of preventing the light leakage, for the color filter 6, black matrices (not shown) are preferably formed at the portions corresponding to the thin film transistor and a storage capacitor 23.

A pair of alignment films 4 inducing homogeneous alignment in direct contact with the liquid-crystal composition constituting the liquid-crystal layer 5 are provided on the electrode layer 3 and the color filter 6.

Here, the alignment direction (alignment direction of liquid-crystal molecules) of the alignment film 4 in the present embodiment will be described with reference to FIG. 4. FIG. 4 is a view schematically showing an alignment direction of a liquid-crystal induced by the alignment film 4. In the present invention, a liquid-crystal composition having negative dielectric anisotropy is used. Therefore, when the vertical direction (direction in which a horizontal electric field is formed) with respect to the line forming a comb shape of the pixel electrode 21 is defined as the x axis, the x axis and the liquid-crystal molecule 30 are preferably disposed such that the angle θ between the x axis and the long axis direction of the liquid-crystal molecule 30 becomes about 0° to 45°. In the example shown in FIG. 3, the angle θ between the x axis and the long axis direction of the liquid-crystal molecule 30 is about 0°. To induce the alignment direction of the liquid-crystal in this manner is for increase in the maximum transmittance of the liquid-crystal display device.

By the alignment film being a photo-alignment film, it is possible to reduce the decrease in alignment restricting force with respect to the liquid-crystal molecules due to rubbing irregularity, and it is possible to provide an FFS mode liquid-crystal display element having excellent transmittance characteristics.

In addition, the polarizing plate 1 and the polarizing plate 8 can be adjusted such that the viewing angle or the contrast is improved by adjusting the polarization axis of each polarizing plate, and the polarizing plate 1 and the polarizing plate preferably have transmission axes orthogonal to each other such that these transmission axes are operated in a normally black mode. In particular, any one of the polarizing plate 1 and the polarizing plate 8 is preferably disposed so as to have a transmission axis parallel to the alignment direction of the liquid-crystal molecule 30. In addition, the product of the refractive index anisotropy Δn of the liquid-crystal and the cell thickness d is preferably adjusted such that the contrast is at a maximum. Furthermore, a phase difference film for widening the viewing angle can also be used.

In addition, in the liquid-crystal display element according to the present invention, it is preferable that the common electrode is formed on almost the entire surface of the first substrate and disposed on the first substrate side rather than the pixel electrode. That is, a preferable embodiment of the liquid-crystal display element according to the present invention has a first substrate and a second substrate disposed to face each other, a liquid-crystal layer containing a liquid-crystal composition with which the gap between the first substrate and the second substrate is filled, an electrode layer including a common electrode including a transparent conductive material, a plurality of gate bus lines and data bus lines disposed in a matrix shape, a thin film transistor provided at the intersection at which the gate bus lines and the data bus lines intersect each other, and a pixel electrode including a transparent conductive material and forming a fringe electric field between the common electrode and the pixel electrode by being driven by the thin film transistor, for each pixel on the first substrate, and photo-alignment film layers inducing homogeneous alignment, which are formed between the liquid-crystal layer and the first substrate and between the liquid-crystal layer and the second substrate, respectively, in which the distance R between the pixel electrode and the common electrode is smaller than the distance G between the first substrate and the second substrate, and the common electrode is formed on almost the entire surface of the first substrate and disposed on the first substrate side rather than the pixel electrode. Moreover, FIGS. 1 to 4 which are a form of the present invention show a form in which the common electrode is formed on almost the entire surface of the first substrate and disposed on the first substrate side rather than the pixel electrode.

The FFS type liquid-crystal display element described with reference to FIGS. 1 to 4 is simply an example, and the present invention can be performed in other various forms within the scope of the technical idea of the present invention,

Another example of the liquid-crystal display element according to the present, invention will be described below with reference to FIGS. 5 and 6.

For example, FIG. 5 is another embodiment of an enlarged plan view of the region surrounded by the II line of the electrode layer 3 formed on the substrate 2 in FIG. 1. As shown in FIG. 5, the pixel electrode 21 may be configured to have a slit. In addition, the pattern of the slit may be formed so as to have a tilt angle with respect to the gate bus line 26 or the data bus line 25.

The pixel electrode 21 shown in FIG. 5 has a shape in which a substantially rectangular plate electrode is hollowed out in a substantially rectangular frame shape notch portion. In addition, the comb tooth shape common electrode 22 is formed on one surface through the insulating layer 18 (not shown) on the back surface of the pixel electrode 21. The shortest distance R between the common electrode and the pixel electrode which are adjacent is shorter than the shortest distance G between the alignment layers. In addition, the surface of the pixel electrode is preferably covered with a protective insulation film and an alignment film layer, in the region surrounded by the plurality of gate bus lines 23 and the plurality of data bus lines 24, a storage capacitor (not shown) for storing a display signal supplied through the data wire 24 may be provided. Moreover, the shape of the notch portion is not particularly limited, and in addition to the substantially rectangular shape shown in FIG. 5, notch portions having a known shape such as an oval shape, a circular shape, a rectangular shape, a diamond shape, a triangular shape, or a parallelogram shape can be used.

FIG. 6 is an embodiment different from FIG. 3, and another example of a sectional view obtained by cutting the liquid-crystal display element shown in FIG. 1 in the III-III line direction in FIG. 2. The first substrate 2 in which an alignment layer 4 and the electrode layer 3 including the thin film transistor 20 are formed on the surface and the second substrate 8 in which the alignment layer 4 is formed on the surface are disposed such that, the alignment layers face each other with a predetermined space D, and the liquid-crystal layer 5 including a liquid-crystal composition fills this space. The gate insulating film 12, the common electrode 22, the insulating film 13, the pixel electrode 21, and the alignment layer 4 are stacked on a part of the surface of the first substrate 2 in this order. In addition, as also shown in FIG. 5, the pixel electrode 21 has a shape in which the central portion and both ends of a flat plate body are hollowed out in a triangular notch portion and the remaining region is hollowed cut in a rectangular notch portion, and the common electrode 22 has a structure in which the comb tooth shape common electrode is disposed on the first substrate side rather than the pixel electrode in substantially parallel to the substantially oval shape notch portion of the pixel electrode 21.

In addition, in the example shown in FIG. 6, the common electrode 22 having a comb shape or a slit is used, and the distance between the pixel electrode 21 and the common electrode 22 becomes R=α. Furthermore, in FIG. 3, an example in which the common electrode 22 is formed on the gate insulating film 12 is shown, but, as shown in FIG. 6, the common electrode 22 is formed on the first substrate 2, and the pixel electrode 21 may be provided through the gate insulating film 12. It is preferable that the electrode width l of the pixel electrode 21, the electrode width n of the common electrode 22, and the distance R between electrodes are suitably adjusted to such an extent that all the liquid-crystal molecules in the liquid-crystal layer 5 can be driven by the electric field generated.

In the FFS mode liquid-crystal display element according to the present invention, since a specific liquid-crystal composition and a specific photo-alignment film are used, it is possible to achieve both high speed response and suppression of display defects.

In addition, in the FFS mode liquid-crystal display element, when the liquid-crystal layer 5 is injected between the first substrate 2 and the second substrate 1, for example, a method such as a vacuum injection method or a drop injection (ODF: One Drop Fill) method is performed, but, in the present invention, in the ODF method, it is possible to suppress generation of drip marks when the liquid-crystal composition is dropped on a substrate. Moreover, the drip mark is defined as a phenomenon in which, in the case of a black display, white mark formed by dropping of the liquid-crystal composition comes up to the surface.

The generation of the drip marks is significantly influenced by a liquid-crystal material which is injected, and is also inevitably influenced by the configuration of the display element. In the FFS mode liquid-crystal display element, the thin film transistor formed in the display element and the pixel electrode 21 having a comb shape or a slit do not have a member which separates the liquid-crystal composition other than the thin alignment film 4 or a thin alignment film 4 and the thin insulation protecting layer and thus, the possibility that the ionic materials cannot be blocked is high, and it is impossible to avoid generation of the drip marks due to the interaction between a metal material configuring the electrode and the liquid-crystal composition, but, by using the liquid-crystal composition and the photo-alignment film of the present invention in an FFS type liquid-crystal display element in combination, the generation of the drip marks is effectively suppressed.

In addition, in the manufacturing process at a liquid-crystal display element according to the ODF method, it is necessary to drop an optimal liquid-crystal injection amount according to the size of the liquid-crystal display element, but, for the liquid-crystal composition of the present invention, for example, effects with respect to a rapid pressure change or impact in a dropping apparatus which occurs when the liquid-crystal is dropped are small, and continuously stably dropping a liquid-crystal over a long period of time is possible, and thus, it is also possible to maintain a high yield of the liquid-crystal display element. In particular, in a small-sized liquid-crystal display element which is frequently used in smartphones in vogue recently, it is difficult to control deviation from the optimal value to be within a certain range since the optimal liquid-crystal injection amount is small, but by using the liquid-crystal composition of the present invention, it is possible to realize the stable discharging amount of liquid-crystal material even in the case of a small-sized liquid-crystal display element.

Hereinafter, the manufacture method of the liquid-crystal display element of the present invention will be described. For example, the liquid-crystal display element of the present invention is preferably manufactured by the following steps (1) to (3).

In the manufacture method of the liquid-crystal display element according to the present invention, it is preferable that after the photo-alignment film precursor solution according to the present invention is applied onto a substrate, by heating the solution-applied surface, a coating film is formed on the substrate (step (1)). In more detail, for example, the photo-alignment film precursor solution of the present invention is applied onto a conductive film formed surface of the substrate provided with a transparent conductive film which has beer, patterned in a comb tooth shape and one surface of the counter substrate not provided with a conductive film, respectively, and then, by heating each coated surface, a coating film is formed.

The photo-alignment film precursor solution according to the present invention is preferably a solution including the photoresponsive decomposition type polymer described above. The photoresponsive decomposition type polymer preferably contains at least ore type of polymer selected from the group consisting of polyamic acid and polyimide obtained by reacting tetracarboxylic dianhydride and a diamine compound, and an organic solvent.

The photo-alignment film precursor solution of the present invention is preferably respectively applied by a offset printing method, a spin coating method, a roll coating method, or an ink jet printing method. As the substrate, for example, a transparent substrate formed of glass such as float glass or soda glass; or plastic such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, or poly(alicyclic olefin) can be used. As the transparent conductive film provided on one surface of (a first) substrate, a NESA film formed of tin oxide (SnO₂), an ITO film formed of indium oxide—tin oxide In₂O₃—SnO₂), or the like may be used. Furthermore, to obtain a transparent conductive film patterned, for example, a method of forming a pattern by photo etching after forming a transparent conductive film without a pattern, a method of using a mask having a desired pattern when forming a transparent conductive film, or the like can be adopted. When application of the photo-alignment film precursor solution is performed, to further improve the adhesion, between the substrate surface or the transparent conductive film and the coating film, the substrata surface may be subjected to a surface treatment in advance by a known method such as a functional silane compound, functional titanium compound, or the like.

After the photo-alignment film precursor solution is applied, prebaking may be performed if necessary, and the pre-baking temperature in this case is preferably 30° C. to 200° C. In addition, the pre-baking time is preferably 0.25 to 10 minutes. Thereafter, the solvent is completely removed, and for the purpose of thermal imidization of the amic acid structure present in the polymer, a firing step is preferably performed, if necessary. The firing temperature at this time is preferably 80° C. to 300° C. The firing time is preferably 5 to 200 minutes. In this manner, the film thickness of the film formed is preferably 0.001 to 1 μm.

In addition, in a case where the polymer included in the photo-alignment film precursor solution of the present invention is an imidized polymer having polyamic acid or an imide ring structure and an amic acid structure, by proceeding a dehydration and ring-closing reaction by further heating after coating film formation, a further imidized coating film may be formed.

In the manufacture method of the liquid-crystal display element according to the present invention, the coating film including polyamic acid or polyimide formed on the substrate is preferably irradiated with light (step (2)). In addition, the step (2) may be performed after a step (3) described below. As the light with which the coating film is irradiated, ultraviolet rays or visible rays including light having a wavelength of 150 to 800 nm cats be used, and ultraviolet rays including light having a wavelength of 300 to 400 nm are preferable.

As the light source of irradiation light, a low pressure mercury lamp, a high pressure mercury lamp, a deuterium lamp, a metal halide lamp, an argon resonance lamp, a xenon lamp, or excimer laser can be used. Moreover, ultraviolet rays in the above-described preferable wavelength region can be obtained by means using a light source in combination with, for example, a filter, a diffraction grating, or the like. The irradiation amount of light is preferably equal to or greater than 1,000 J/m² and equal to or less than 100,000 J/m².

In the manufacture method of the liquid-crystal display element according to the present invention, it is preferable that a pair of substrates on which a photo-alignment film or a coating film has been formed are disposed to face each other through a gap (cell gap), and the gap is filled with the liquid-crystal composition according to the present invention (step (3)).

Examples of the method of filling with the liquid-crystal composition include (1) a vacuum injection method (a method of configuring liquid-crystal cells by disposing a pair of substrates on which a photo-alignment film or a coating film has been formed to face each other through a gap (cell gap) such that the alignment directions of the films on two substrates become orthogonal, by attaching the peripheral portions of the two substrates with a sealing agent, by filling the cell gap with a liquid-crystal by injecting the liquid-crystal into the cell gap partitioned by the substrate surface and the sealing agent, and by sealing the injection hole) and (2) an ODF method. In the method of introducing a liquid-crystal composition by the vacuum injection method, drip marks are less likely to be generated, but with the increase in a substrate size, there is a problem in the manufacturing time, cost, or the like. However, in the present invention, the display element which is manufactured in combination of a photo-alignment film and a liquid-crystal composition by the ODF method can be more suitably used.

In addition, since, in the FFS mode as in the present invention, the electrode layer 3 (a surface covered with a photo-alignment film) such as TFT is formed on the surface of the same substrate (in FIG. 3, the first substrate), a large number of unevenness are present on the surface, and an environment in which generation of drip marks is likely to be promoted is formed, but by combining a photo-alignment film and a liquid-crystal composition, this problem is thought to be alleviated.

EXAMPLES

Hereinafter, the present invention will be described in more detail with examples, and the present invention is not limited to the examples. In addition, “% ” in the compositions of the following examples and comparative examples means “% by mass”.

In the examples, the measured characteristics are as follows.

T_(NI): nematic phase-isotropic liquid phase transition temperature (° C.)

Δn: refractive index anisotropy at 25° C.

Δ∈: dielectric anisotropy at 25° C.

η: viscosity (mPa·s) at 20° C.

γ₁: rotational viscosity (mPa·s) at 25° C.

VHR: voltage holding ratio (%) at 60° C. under the conditions of a frequency of 60 Hz and an applied voltage of 1 V.

Burn-In:

After displaying a predetermined fixed pattern in the display area for 1,000 hours, by visually inspecting the residual image level of the fixed pattern at the time when full screen was uniformly displayed, the evaluation of the burn-in on a liquid-crystal display element was performed on a scale of four stages described below.

A: Residual image was not observed

B: Residual image was very slightly observed, however it was an acceptable level

C: Residual image was observed, and it was an unacceptable level

D: Residual image was observed, and it was a very severe level

Drip Marks:

By visually observing drip marks appeared in white when the entire screen was displayed in black, the evaluation at the drip marks on a liquid-crystal display device was performed on a scale of four stages described below.

A: Residual image was not observed

B: Residual image was very slightly observed, however it was an acceptable level

C: Residual image was observed, and it was an unacceptable level

D: Residual image was observed, and it was a very severe level

Process Adaptability:

In ODF process, dropping the liquid-crystal by 50 pL at one time was performed 100,000 times using a constant volume measuring pump, and the change in amount of liquid-crystal dropped by each 100 times of the following “0 to 100 times, 101 to 200 times, 201 to 300 times, . . . , 99, 901 to 100,000 times” was evaluated on a scale of four stages described below.

A: Change was extremely small (liquid-crystal display element could be stably manufactured)

B: Change was slightly observed, but it was an acceptable level

C: Change was observed, and it was an unacceptable level (yield was deteriorated by generation of spots)

D: Change was observed, and it was a very severe level (liquid-crystal leakage or vacuum bubbles were generated)

Solubility at Low Temperatures:

After preparing a liquid-crystal composition, 1 g of the liquid-crystal, composition was weighed and placed in a sample bottle of 2 mL, the temperature change having the cycle of “−20° C. (maintained for 1 hour)→heating (0.1° C./min)→20° C. (maintained for 1 hour)→heating (0.1° C./min)→20° C. (maintained for 1 hour) →cooling (−0.1° C./min)→0° C. (maintained for 1 hour)→cooling (−0.1° C./min)→−20° C.” was continuously given thereto in a temperature controlled test chamber, the generation of precipitates from the liquid-crystal composition was visually observed, and the solubility evaluation at low temperatures was performed on a scale of four stages described below.

A: Precipitates were not observed for equal to or longer than 600 hours.

B: Precipitates were not observed for equal to or longer than 300 hours.

C: Precipitates were observed within 150 hours.

D: Precipitates were observed within 75 hours.

Moreover, in the examples, the following abbreviations were used for describing the compounds.

(Side Chain)

-   -   n -CnH2n+1 a linear alkyl group having n carbon atoms     -   On -OCnH2n+1 a linear alkoxy group having n carbon atoms     -   V —C═CH2 a vinyl group     -   Vn —C═C—CnH2n+1 1-alkene having (n+1) carbon atoms

(Ring Structure)

Example 1 Liquid-Crystal Composition 1

The liquid-crystal composition (liquid-crystal composition 1) having the compositional ratio described below was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

Using the liquid-crystal composition of the present invention, an FFS mode liquid-crystal display element having a cell thickness of 3.0 μm which is general for a TV was prepared, and an alignment film was prepared in the following manner.

<Photodecomposition Type Photo-Alignment Film>

“Photo-Alignment Film 1”

1.0 mol % of p-phenylenediamine was dissolved in N-methyl-2-pyrrolidone, and 1 mol % of cyclobutane tetracarboxylic dianhydride was added thereto, and the resultant was allowed to react at 20° C. for 12 hours, whereby polyamic acid varnish having a standard polystyrene conversion weight average molecular weight of about 100,000 and a weight average molecular weight/number average molecular weight (Mv/Mn) of about 1.6 was obtained. Next, after this polyamic acid varnish was diluted to a concentration of 6%, 0.3% by weight of γ-aminopropyltriethoxysilane as a solid content was added thereto, and the resultant was printed on a first thin film laminate and a second thin film laminate, followed by heating at 210° C. for 30 minutes, whereby a photodecomposition type insulating film (polyimide film) was formed.

Thereafter, the photodecomposition type polyimide film was subjected to, for example, alignment processing of irradiating with light (ultraviolet rays) from a polarised UV lamp having an emission line in a wavelength range of 240 nm to 400 nm. In this alignment processing, for example, irradiation was performed at an irradiation energy of about 4 J/cm² with linearly polarized light having a polarization ratio of about 20:1, which was obtained from ultraviolet rays from a high pressure mercury lamp using a pile polarizer obtained by stacking quartz substrates.

“Photo-Alignment Film 2”

(Synthesis of Polyamic Acid A)

1.0 mol % of 4,4′-diaminodiphenyl ether was dissolved in N-methyl-2-pyrrolidone, and 1 mol % of cyclobutane tetracarboxylic dianhydride was added thereto, and the resultant was allowed to react at 20° C. for 12 hours, whereby a solution of a polyamic acid A having a standard polystyrene conversion weight average molecular weight of about 50,000 and a weight average molecular weight/number average molecular weight (Mv/Mn) of about 1.6 was obtained.

(Synthesis of Polyamic Acid B)

1.0 mol % of 4,4′-diaminodiphenylamine was dissolved in N-methyl-2-pyrrolidone, and 1 mol % of cyclobutane tetracarboxylic dianhydride was added thereto, and the resultant was allowed to react at 20° C. for 6 hours, whereby a solution of a polyamic acid B having a standard polystyrene conversion weight average molecular weight of about 55,000 and a weight average molecular weight/number average molecular weight (Mv/Mn) of about 1.9 was obtained.

(Preparation of Mixture)

The polyamic acid A solution and the polyamic acid B solution were mixed such that the solid content mass ratio became 1:1, and the resultant was diluted with a mixed solvent of N-methyl-2-pyrrolidone and 2-butoxyethanol having a mass ratio of 1:1, whereby a polyamic acid solution was obtained.

The polyamic acid solution was printed on the first thin film laminate and the second thin film laminate, and heated to 230° C. for 30 minutes, whereby a photodecomposition type insulating film (polyimide film) was formed. Thereafter, irradiation was performed on the photodecomposition type polyimide film at an irradiation energy of about 0.5 J/cm² with linearly polarized light having an extinction ratio of about 100:1, which was obtained from light (ultraviolet rays) from a high pressure ultraviolet lamp using a wire-grid polarizer.

“Photo-Alignment Film 3”

(Preparation of Solution for Photo-Alignment Film)

32.40 g of N-methyl-2-pyrrolidone was added to 3.24 g of 1,4-phenylenediamine, and the resultant was stirred to be dissolved while blowing nitrogen thereto. While stirring this diamine solution, 7.81 g of cyclobutane tetracarboxylic dianhydride was added thereto, then, 78.03 g of N-methyl-2-pyrrolidone was further added thereto, and the resultant was stirred at 30° C. for 18 hours in a nitrogen atmosphere to perform the reaction. Furthermore, 62.68 g of a mixed solvent of N-methyl-2-pyrrolidone and 2-butoxyethanol having a mass ratio of 1:1 was added thereto at ordinary temperature for dilution, and the resultant was stirred, whereby a solution for a photo-alignment film was obtained.

(Formation of Liquid-Crystal Alignment Film)

(Formation of Photodecomposition Type Resin Film)

The solution for a photo-alignment film was applied onto a comb shape transparent electrode formed on a first substrate by a spin coating method, whereby a resin film having a dry film thickness of 0.1 μm was formed. An alignment film was formed on a second substrate also in the same manner.

The substrate on which the resin film had been formed was heated at 230° C. for 30 minutes to perform the reaction, whereby a photodecomposition type resin film (polyimide film) was formed.

(Alignment Processing)

Thereafter, ultraviolet rays having a wavelength of 256 nm were taken out from a high pressure mercury lamp using a band pass filter, then, linearly polarized light having an extinction ratio of about 100:1 was obtained using a wire-grid polarizer, and photo-alignment processing was performed on the photodecomposition type resin film by irradiation with an irradiation energy of about 1.0 J/cm². Thereafter, firing was performed at 230° C. for 30 minutes to remove the impurities produced by decomposition, and the polyimide film was washed with pure water and dried, whereby a glass substrate on which a photodecomposition type alignment film had been formed was obtained.

<Photodimerization Type Photo-Alignment Film>

“Photo-Alignment Film 4”

(Synthesis of Monomer)

Synthesis Example 1

By the method shown in the following scheme, a target mononer (I-1-1) was synthesized through intermediates of compounds 1 to 6.

Synthesis of Compound 1

199 g (1.21 mol) of 8-chlorooctanol, 158.3 g (1.84 mol) of methyl methacrylate, 1.5 g of 4-methoxyphenol, and 22.8 g (0.12 mol) of p-toluenesulfonic acid were dissolved in 450 mL of cyclohexane, and the resultant was heated to reflux for 6 hours. After the reaction solution was cooled to room temperature, the solution was washed three times with water, three times with a saturated sodium hydrogen carbonate aqueous solution, and two times with a saturated saline solution. The solution was dried over anhydrous sodium sulfate, and the solvent was distilled off, whereby 258 g of a compound 1 (8-chlorooctyl methacrylate) was obtained as colorless and transparent liquid. Purity of 99% (GC). EI-MS: 232[+]

Synthesis of Compound 2

34.6 g (0.284 mol) of 4-hydroxybenzaldehyde, 49 g (0.341 mol) of potassium carbonate, and 0.1 g of 18-crown-6 were dissolved in 500 mL of dimethylformamide, and 58 g (0.284 mol) of 8-chlorooctyl methacrylate was added thereto at room temperature in a nitrogen atmosphere. The reaction solution was heated to 90° C. and stirred for 6 hours. It was confirmed using GC that the reaction ended, and the reaction solution was cooled to room temperature and filtered. 200 mL of ethyl acetate and 200 mL of water were added thereto, and the resultant was filtered again. The organic layer and the aqueous layer were separated, then, ethyl acetate was added to the aqueous layer, and extraction was performed three times. All the organic layers were collected, and washed three times with a saturated saline solution. To dry the organic layer, anhydrous sodium sulfate was added thereto, and the solvent was distilled off, whereby a crude compound 2 was obtained. The obtained compound 2 was used in the next reaction without specific purification.

EI-MS: 318[M⁺]

Synthesis of Compound 3

50 g (about 0.14 mol) of the compound 2, 4.43 g (0.029 mol) of sodium dihydrogen phosphate, and 16 g of 30% hydrogen peroxide water were dissolved in a mixture of 60 mL of water and 350 mL of acetonitrile, and the resultant was cooled with ice. Then, a solution obtained by diluting 23 g of 78% sodium chlorite with 200 mL of water was added dropwise to the reaction solution, and the reaction solution was stirred at room temperature overnight. It was confirmed using HPLC that the reaction ended. 10% hydrochloric acid was added to the reaction solution until the pH became 1, and the precipitated white solid was separated by filtration. The obtained solid was washed three times with water. The obtained solid was dissolved in dichloromethane, and anhydrous sodium sulfate was added thereto to dry the resultant. Heptane was added to the solution, then, the dichloromethane was distilled off under reduced pressure, and the precipitated solid was separated by filtration, whereby 30 g of a target compound 3 was obtained. Purity of 99% (HPLC).

Synthesis of Compound 4

50 g (0.246 mol) of 4-bromo-2-methoxyphenol, 47.2 g (0.369 mol) of t-butyl acrylate, and 50.9 g (0.369 mol) of potassium carbonate were dissolved in 700 mL of N-methylpyrrolidone, and the system was purged with nitrogen. 0.055 g (0.246 mmol) of palladium acetate was added to the reaction solution, and the system was purged with nitrogen again and stirred at 130° C. for 6 hours. It was confirmed using HPLC that the reaction ended. After the reaction solution was cooled to room temperature, 300 mL of ethyl acetate and 300 mL of 5% hydrochloric acid were added to this. The organic layer and the aqueous layer were separated, then, ethyl acetate was added to the aqueous layer, and extraction was performed. All the organic layers were collected, then, washed three times with a saturated saline solution, and dried over anhydrous sodium sulfate. The solvent was distilled off, and 80 g of silica gel was added thereto to form slurry. A column of 100 g of alumina/300 g of silica gel was filled with this and elution was performed with an ethyl acetate/heptane mixed solution. The solvent was distilled off, and the obtained crude crystal was recrystallized from heptane, whereby 43.2 g of a compound 4 was obtained as a white solid. Purity of 99%(HPLC). EI-MS: 250[M+]

Synthesis of Compound 5

22.3 g (0.06676 mol) of the compound 3, 16.7 g (0.06677 mol) of the compound 4, and 1.22 g (10 mmol) of 4-dimethylaminopyridine were dissolved in 400 mL of dichloromethane, and the system was purged with nitrogen and cooled with ice. Then, a solution obtained by dissolving 12.6 g (0.1 mol) of N,N′-diisopropylcarbodiimide in 100 mL of dichloromethane was added dropwise to the reaction solution, and the resultant was stirred at room temperature overnight. The reaction solution was filtered, washed with 200 mL of 10% hydrochloric acid, washed three times with 200 mL of a saturated saline solution, and dried over anhydrous magnesium sulfate. After the solvent was distilled off to some extent, 70 g of silica gel was added thereto to form slurry, and a column of 100 g of alumina/200 g of silica gel was filled with this slurry and elution was performed with dichloromethane. The solvent was distilled off, and the resultant was recrystallized from a mixed solvent of ethyl acetate/heptane, whereby 31.8 g of a target compound 5 was obtained as a white solid. Purity of 99% (HPLC). EI-MS: 566[M+]

Synthesis of Compound 6

31.8 g (0.0562 mol) of the compound 5 was dissolved in 200 mL of dichloromethane, and the system was purged with nitrogen and cooled with ice. 32 g (0.280 mol) of trifluoroacetic acid was added dropwise to the system, followed by stirring at room temperature overnight. It was confirmed using HPLC that, the reaction ended. 300 mL of heptane was added to the reaction solution, then, a solid was precipitated by distilling the solvent off, and the solid was separated by filtration. The obtained solid was washed with water and heptane, whereby 26 g of a target compound 6 was obtained as a colorless crystal. Purity of 95% (HPLC).

Synthesis of Monomer (I-1-1)

22.9 g (45 mmol) of the compound 6, 4.9 g (0.04 mol) of 3-hydroxypropionitrile, and 0.70 g (5.6 mmol) of 4-dimethylaminopyridine were dissolved in 200 mL of dichloromethane, and the system was purged with nitrogen and cooled with ice. Then, a solution obtained by dissolving 7.87 g (64 mmol) of N,N′-diisopropylcarbodiimide in 50 mL of dichloromethane was added dropwise to the reaction solution, and the resultant was stirred at room temperature overnight. The reaction solution was filtered, washed with 100 mL of 10% hydrochloric acid, washed three times with 100 mL of a saturated saline solution, and dried over anhydrous magnesium sulfate. Purification was performed by using a column of 30 g of alumina/300 g of silica gel and a mixed solution of ethyl acetate/dichloromethane. The solid obtained by distilling the solvent off was recrystallized from methanol, whereby 16.4 g of a target monomer (I-1-1) was obtained as a white solid. Purity of 99.5% (HPLC).

EI-MS: 563[M+]

Synthesis of Polymer (PA-1)

10 parts of the monomer (I-1-1) was dissolved in 45 parts of tetrahydrofuran (THF), then, 0.03 parts of azobisisobutyronitrile (AIBN) was added thereto, and the obtained solution was heated to reflux for 8 hours in a nitrogen atmosphere to perform the reaction. Next, after the solution after the reaction was added dropwise to 600 parts of methanol, followed by stirring, the precipitate was collected and dissolved in 50 parts of THF, then, the resultant was added dropwise to 1,200 parts of ice-cooled hexane, followed by stirring, and the precipitated solid was collected. The obtained solid was dissolved in 50 parts of THF, then, the resultant was added dropwise to 1,200 parts of ice-cooled methanol, followed by stirring, and the precipitated solid was collected, dissolved in THF, and vacuum-dried, whereby a polymer (PA-1) was obtained. The weight average molecular weight (Mw) of the obtained polymer (PA-1) was 383,000, and the molecular weight distribution (Mw/Mn) was 2.75.

Moreover, adjustment of the molecular weight of the polymer was performed by adjusting the heating and refluxing time in a nitrogen atmosphere and measuring the weight average molecular weight (Mw).

(Measurement of Molecular Weight)

Mw and Mn were measured by GPC (Gel Permeation Chromatography) under the following measurement conditions.

As the measuring apparatus, GPC apparatus HLC-8220GPC manufactured by Tosoh Corporation was used, as the analytical column, four columns, that is, TSKgel GMHXL×2, TSKgel G2000XL×1, and TSKgel G1000XL×1 were used in a state of being connected in series, as the detector, a differential refractive index (RI) detector was used, and as the standard sample for creating a calibration curve, polystyrene standard sample STANDARD SM-105 (molecular weight range of 1,300 to 3,800,000) manufactured by Showa Denko K.K. was used. The obtained polymer was dissolved in THF to be a concentration of 1 μg/mL, and measurement was performed on the resultant under the conditions of a mobile phase of THF, a feed rate of 1 mL/min, a column temperature of 40° C., and a sample injection volume of 300 μL.

(Measurement of Glass Transition Temperature)

The glass transition temperature was measured using a differential scanning calorimeter (DSC). As the measuring apparatus, DSC equipment DSC6220 manufactured by Seiko Instruments Inc. was used. About 4 mg of a polymer sample was put into an aluminum pan and sealed, and when the temperature was raised from −20° C. to 180° C. at a rate of 10°/min, the baseline shift due to glass transition was observed. The transition starting point was read from the intersection point of tangential lines, and the point was taken as the glass transition temperature (Tg).

(Formation of Liquid-Crystal Alignment Film)

(Preparation of Photodimerization Type Resin Film)

A mixture of 5 parts of the polymer (PA-1), 47.5 parts of H-methylpyrrolidone, and 47.5 parts of 2-butoxyethanol was stirred at room temperature for 10 minutes to be homogeneously dissolved. Next, the solution was applied onto a glass substrate using a spin coater and dried at 100° C. for 3 minutes, whereby a film was formed on the glass substrate. When the formed film was visually observed, it was confirmed that a smooth film was formed.

(Photo-Alignment Processing)

Next, the formed film was irradiated (amount of light irradiation of 100 mJ/cm²) with linearly polarized light (illuminance: 10 mW/cm²) of ultraviolet light (wavelength of 313 nm) for 10 seconds from the vertical direction using a polarized light irradiating apparatus provided with an ultra high pressure mercury lamp, a wavelength cut filter, a band pass filter, and a polarizing filter, whereby a photo-alignment film was obtained. A firing treatment and a washing treatment were not required. The dry film thickness of the resin film was 0.1 μm.

<Photoisomerization Type Photo-Alignment Film>

“Photo-Alignment Film 5”

Synthesis Example 1 Synthesis of Dichroic Compound (a)

230 ml of 2% hydrochloric acid was added to 8.6 g (25 mmol) of 2,2′-benzidinedisufonic acid, then, an aqueous solution of 3.5 g (51 mmol) of sodium nitrite was added dropwise thereto little by little while maintaining the temperature at 0° C. to 5° C., and the resultant was allowed to react for 2 hours, whereby a diazonium salt was prepared. Next, 6.9 g (50 mmol) of salicylic acid was dissolved in 300 ml of a 5% sodium carbonate aqueous solution, and the above diaxonium salt mixture was slowly added dropwise thereto. After the resultant was allowed to react for 1 hour, a 20% saline solution was added thereto, whereby precipitate was obtained. This precipitate was recrystallized from a mixed solvent of ethanol and water, whereby 4.8 g of the azo compound represented by Formula (a) was obtained.

(Composition for Examples: Preparation of Composition (1) for Photo-Alignment Film)

2 parts of the compound represented by Formula (a) was dissolved in 98 parts of N-methyl-2-pyrrolidone (NMP) (solution A). 98 parts of 2-butoxyethanol (BC) was added to 2 parts of methylated melamine, Sumimal M-100C (hereinafter, M-100C) (manufactured by Chang Chun Plastics Co., LTD., a hexamethoxymethylated melamine mononer having a molecular weight of 390 and an average degree of polymerization of 1.3 to 1.7), whereby a homogeneous solution was obtained (solution B). 100 parts of the solution A, 23 parts of the solution B, and 77 parts of BC were mixed, whereby a solution having a solid content ratio of 1.0% was prepared. The obtained solution was filtered through a membrane filter having a pore size of 0.45 μm, whereby a composition (1) for a photo-alignment film was obtained.

(Formation of Liquid-Crystal Alignment Film)

(Preparation of Photoisomerization Type Resin Film)

The composition (1) for a photo-alignment film was applied onto a glass substrate using a spin coater and dried at 100° C. for 1 minute.

(Photo-Alignment Processing)

The surface of the obtained coating film was irradiated with linearly polarized light and parallel light of ultraviolet light (irradiation intensity: 10 mW/cm²) of a wavelength of around 365 nm with irradiation energy of 100 mJ/cm² from the direction perpendicular to the glass substrate through a wavelength cut filter and a polarizing filter on an ultra high pressure mercury lamp, whereby a photo-alignment film was obtained. A firing treatment and a washing treatment were not required. The dry film thickness of the resin film was 0.1 μm.

<Rubbing Type Alignment Film>

(Rubbing Type Alignment Film)

(Formation of Rubbing Type Polyimide Liquid-Crystal Alignment Film)

(Preparation of Alignment Film Solution)

59.72 g of N-methyl-2-pyrrolidone was added to 5.98 g of 4,4′-diaminodiphenylamine, and the resultant was stirred to be dissolved while blowing nitrogen thereto. While stirring this diamine solution, 6.54 g of pyromellitic dianhydride was added thereto, then, 65.30 g of N-methyl-2-pyrrolidone was further added thereto, and the resultant was stirred at 30° C. for 18 hours in a nitrogen atmosphere to perform the reaction. Furthermore, 71.06 g of a mixed solvent of N-methyl-2-pyrrolidone and 2-butoxyethanol having a mass ratio of 1:1 was added thereto at ordinary temperature for dilution, and the resultant was stirred, whereby a polyamic acid solution was obtained.

(Formation of Liquid-Crystal Alignment Film)

(Preparation of Resin Film)

An alignment film solution was applied onto the first substrate and the second substrate using a spin coater, and the resultant was reacted by being heated at 230° C. for 30 minutes, whereby an insulating film of polyimide was formed.

(Alignment Processing)

The alignment processing was performed by rubbing the surface of the alignment film formed on the substrate in one direction by rotating a roller wound with buff cloth in the direction opposite to the substrate transport direction. The rotation speed of the roller was 600 rpm, the transport speed of the substrate was 5 mm/sec, and the indentation depth with respect to the substrate surface of the buff cloth was 0.3 mm. Thereafter, to remove the scraps of the alignment film or the fiber pieces of the buff cloth ground by rubbing, the polyimide film was washed with pure water and dried.

(Evaluation of Display Quality)

By the alignment film being a photo-alignment film, it is possible to reduce the decrease in alignment properties with respect to the liquid-crystal Molecules due to rubbing irregularity, and it is possible to provide an FFS mode liquid-crystal display element having excellent transmittance characteristics. Since the evaluation of liquid-crystal alignment properties due to various photo-alignment films was performed, the evaluation method thereof will be described below.

A thin film transistor and a transparent electrode layer are formed on the first substrate, and an alignment film is formed thereon. If performing alignment processing by a rubbing method which is a contact method, random scratches are formed on the surface of the alignment film by rubbing. In particular, in the first substrate on which a thin film transistor or a transparent electrode layer pattern has been formed, deeper scratches due to steps due to the thin film transistor or the transparent electrode layer pattern and the diameter (several tens of μm) of the fiber of buff cloth of the rubbing roller are likely to be formed along the steps. Since, at the areas where the scratches have been formed, the liquid-crystal molecules cannot be arrayed in a certain direction at the time of electric field off, light leakage occurs in the liquid-crystal panel at the time of displaying black. As a result, a contrast of equal to or greater than a certain value is less likely to be obtained.

Furthermore, in the resolution mode called 4K recently put into practical use, as the calculation example of a 40-inch panel, 1 pixel size becomes 0.23 mm. In addition, in the resolution mode called 8K recently put into practical use, as the calculation example of a 40-inch panel, 1 pixel sire becomes fine to the extent of 0.11 mm. That is, since 1 pixel size is close to the diameter of the fiber of buff cloth of the rubbing roller, there is a concern that, by the scratches formed at the time of being subjected to alignment processing by a rubbing method, in a pixel unit or an intermittent pixel array unit, the areas where the liquid-crystal molecules can not be arrayed in a certain direction at the time of electric field off were generated, and significant decrease in contrast due to a large amount of light leakage at the time of displaying black or a large number of display defects is caused.

Since scratches are not generated on the surface of the alignment film, by performing alignment processing in a non-contact by a photo-alignment method, it is possible to achieve clear black display in which there is no light leakage and the contrast is high.

The alignment film solution was applied onto a comb shape transparent electrode formed on the first substrate by a spin coating method, whereby an alignment film having a dry film thickness of 0.1 μm was formed. An alignment film was formed on the second substrate also in the same manner.

(Preparation of Liquid-Crystal Cell)

Using a glass substrate provided with the liquid-crystal alignment film, liquid-crystal cells were prepared. Mote specifically, the first substrate and the second substrate on which alignment films are formed respectively are disposed such that the respective liquid-crystal alignment films face each other and the direction in which irradiation with linearly polarized light was performed or rubbing was perforated becomes an anti-parallel direction (180°), and while maintaining a certain gap (4 μm) between the two substrates, the peripheral portions thereof were adhered with a sealing agent. Next, the cell gap partitioned by the surface of the liquid-crystal alignment film and the sealing agent was filled with the following liquid-crystal composition (liquid-crystal compositions 1 to 9) at a temperature just exceeding a transparent point by a dropping method, and then, the resultant was cooled to room temperature, whereby liquid-crystal cells were prepared. Using the liquid-crystal cells prepared in this manner as elements for evaluation, evaluation of display quality due to static contrast was performed.

(Evaluation Method of Static Contrast)

The static contrast (CRS) was measured by the following method.

The above-described optical film which was a measurement object was disposed between the polarizer and the detector of an optical measuring apparatus (RETS-100, manufactured by Otsuka Electronics Co., Ltd.) provided with a white light source, a spectrometer, a polarizer (incident side polarizing plate), an analyzer (emission side polarizing plate), and a detector. Here, in a state in which the rotation angle of the polarizer and the analyzer is 0 degrees (the polarization direction of the polarizer and the analyzer is a parallel position [parallel Nicol]), while rotating the optical film, the light quantity of the transmitted light was detected using the detector, and the light quantity (the light quantity at the time of on) of the transmitted light at the rotation position (the polarization direction of the polarizer and the molecular long axis direction of the polymerizable liquid-crystal are parallel) of the optical film where the detected light quantity is greatest was taken as Yon. In addition, the light quantity (the light quantity at the time of off) of the transmitted light when the rotation angle of the analyzer with respect to the polarizer is 90 degrees (the polarization directions of the polarizer and the analyzer are orthogonal positions crossed Nicholl) while fixing the positions of the polarizer and the optical film was taken as Yoff. The contrast CRS was determined by the following equation (Equation 1). CRS=Yon/Yoff  (Equation 1)

It shows that as the numerical value of the static contrast CRS of (Equation 1) is larger, the light quantity at the time of off, Yoff, is smaller, that is, since light leakage is small, black display is excellent.

In addition, injection of the liquid-crystal composition was performed by a dropping method, and the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated.

Moreover, symbols on the left side of the content represent the abbreviations of the above-described compounds.

[Chem. 49] Example 1

3CyCyV 31%

3CyCyV1 11%

3CyPh5O2 13%

5CyPh5O2  6%

3CyCyPh5O2 11%

2CyPhPh5O2  5%

3CyPhPh5O2 10%

3PhPh5Ph2 13%

TABLE 1 T_(NI)/° C. 75.6 Δn 0.109 n_(o) 1.483 Δε −3.07 ε_(⊥) 6.62 η/mPa · s 15.2 γ₁/mPa · s 98 γ₁/Δn² × 10⁻³ 8.2 γ₁/Δn²/|Δε| 2.69 Initial voltage holding ratio/% 99.6 Voltage holding ratio at 150° C. after 1 hour/% 99.0 Burn-in evaluation A Drip mark evaluation A Process adaptability evaluation A Solubility evaluation at low temperature A

It is understood that the liquid-crystal composition 1 has a T_(NI) of 75.6° C. which is practical, as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 1, an FFS mode liquid-crystal display element was prepared, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Example 2 Liquid-Crystal Composition 2

A liquid-crystal composition (liquid-crystal composition 2) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal composition 1, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

Using the liquid-crystal composition 2, an FFS mode liquids-crystal display element was prepared in the same manner as in Example 1, and the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated, and the results are shown in the same Table.

TABLE 2 Example 2 3CyCyV 32% 3CyCyV1 12% 3CyCyPh1  4% 3CyPh5O2  7% 3PhPh5O2 10% 3CyCyPh5O2 10% 4CyCyPh5O2  2% 2CyPhPh5O2  5% 3CyPhPh5O2  8% 3PhPh5Ph2  5% 4PhPh5Ph2  5% T_(NI)/° C. 76.6 Δn 0.110 n_(o) 1.485 Δε −3.03 ε_(⊥) 6.36 η/mPa · s 13.6 γ₁/mPa · s 90 γ₁/Δn² × 10⁻³ 7.4 γ₁/Δn²/|Δε| 2.45 Initial voltage holding ratio/% 99.5 Voltage holding ratio at 150° C. after 1 hour/% 99.0 Burn-in evaluation A Drip mark evaluation A Process adaptability evaluation A Solubility evaluation at low temperature A

It is understood that the liquid-crystal composition 2 has a liquid-crystal phase temperature range which is practical as a liquid-crystal composition for a TV, a great absolute value of the dielectric anisotropy, and a low viscosity and an optimal Δn. Using the liquid-crystal composition 2, an FFS mode liquid-crystal display element was prepared in the same manner as in Example 1, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Example 3 Liquid-Crystal Composition 3

A liquid-crystal composition (liquid-crystal composition 3) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 1 and 2, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

Using the liquid-crystal composition 3, an FFS mode liquid-crystal display element was prepared in the same manner as in Example 1, and the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated, and the results are shown in the same Table.

TABLE 3 Example 3 3CyCyV 35% 3CyCyV1 12% 3CyCyPh1  2% 3CyPhPh2  6% 3CyPh5O2  4% 3PhPh5O2 10% 5PhPh5O2  4% 3CyCyPh5O2  3% 2CyPhPh5O2 12% 3CyPhPh5O2 12% T_(NI)/° C. 76.1 Δn 0.110 n_(o) 1.486 Δε −3.09 ε_(⊥) 6.45 η/mPa · s 12.2 γ₁/mPa · s 81 γ₁/Δn² × 10⁻³ 6.7 γ₁/Δn²/|Δε| 2.17 Initial voltage holding ratio/% 99.6 Voltage holding ratio at 150° C. after 1 hour/% 99.2 Burn-in evaluation A Drip mark evaluation A Process adaptability evaluation A Solubility evaluation at low temperature A

It is understood that the liquid-crystal composition 3 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 3, an FFS mode liquid-crystal display element was prepared in the same manner as in Example 1, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Comparative Examples 1 to 3

Using the liquid-crystal compositions 1 to 3, vertical alignment liquid-crystal display elements (VA mode liquid-crystal display elements) having a cell thickness of 3.5 μm which is general for a TV were prepared (in all the elements, the same photo-alignment film 1 was used).

Comparisons of transmittances, contrast ratios, response speeds were performed on the FFS mode liquid-crystal display element prepared in each of Examples 1 to 3 and the VA mode liquid-crystal display element prepared in each of Comparative Examples 1 to 3. The results are shown below. Moreover, the transmittance of each of the liquid-crystal display elements in Examples 1 to 3 and Comparative Examples 1 to 3 is a value when the transmittance of an element before the liquid-crystal composition in each mode is injected is defined as 100%.

TABLE 4 Comparative Comparative Comparative Example 1 Example 1 Example 2 Example 2 Example 3 Example 3 Display mode n-FFS VA n-FFS VA n-FFS VA Liquid-crystal Liquid-crystal Liquid-crystal Liquid-crystal composition composition 1 composition 2 composition 3 used Maximum 89% 87% 90% 86% 90% 87% transmittance Contrast ratio 289 280 293 277 302 288 Response speed/ 4.7 8.3 4.4 7.6 3.7 6.6 ms

The FFS mode display elements prepared using the liquid-crystal compositions 1 to 3 (in all of Examples 1 to 3, the same photo-alignment film 1 was used) exhibit characteristics excellent in the maximum transmittance, the contrast ratio, and the response speed, compared to each of VA mode liquid-crystal display elements (Comparative Examples 1 to 3) prepared using the same liquid-crystal composition, respectively.

In the FFS mode liquid-crystal display element in which the liquid-crystal molecules are aligned in parallel to the substrate and a fringe electric field occurs, basic characteristics of a liquid-crystal different from the VA mode liquid-crystal display element in which the liquid-crystal molecules are aligned vertically to the substrate and an electric field occurs vertically are required. By the liquid-crystal compositions 1 to 3 containing General Formula (I), improvement of transmittance which is a significant feature of the FFS mode is achieved without impairing the basic characteristics as a liquid-crystal display element. On the other hand, due to these differences in the FFS mode, effects such as burn-in and drip marks are difficult to be predicted from knowledge in the related art. In the liquid-crystal display element of the present invention, good characteristics are exhibited also in these points.

In addition, Comparisons of transmittances, contrast ratios, response speeds were performed on Examples (Example 1B and Examples 21 to 29) and Comparative Examples (Comparative Example 1B and Comparative Example 2B), in which the type of photo-alignment film was changed, in the following Tables 2 and 3. The results are shown in the following Table 2.

TABLE 2 Example Example Example Example Example Example 1B 21 22 23 24 25 Display mode n-FFS VA n-FFS VA n-FFS VA Alignment film Photo-alignment Photo-alignment Photo-alignment film 3 film 4 film 5 Liquid-crystal Liquid-crystal Liquid-crystal Liquid-crystal composition used composition 1 composition 1 composition 1 Maximum 89% 87% 90% 87% 91% 87% transmittance Contrast ratio 289 280 297 281 287 269 Response speed/ 4.7 8.3 4.4 7.4 4.5 8.1 ms

TABLE 3 Example Example Example Example Comparative Comparative 26 27 28 29 Example 1B Example 2B Display mode n-FFS VA n-FFS VA n-FFS VA Alignment film Photo-alignment Photo-alignment Rubbing alignment film film 6 film 2 Liquid-crystal Liquid-crystal Liquid-crystal Liquid-crystal composition composition 1 composition 1 composition 1 used Maximum 89% 85% 90% 88% 90% 87% transmittance Contrast ratio 288 270 293 282 212 194 Response speed/ 4.4 8.2 4.9 8.6 4.5 7.6 ms

The FFS mode display element (Example) prepared by forming a photo-alignment film exhibited characteristics excellent in contrast compared to the FFS mode display element (Comparative Example) prepared by forming a rubbed alignment film using the same liquid-crystal composition, respectively.

Example 4 Liquid-Crystal Composition 4

A liquid-crystal composition (liquid-crystal composition 4) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the compositions 1 to 3, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 7 Example 4 3CyCy2 25% 3CyCy4  8% 3CyCy5  5% 3CyPh5O2 10% 5CyPh5O2  9% 3CyCyPh5O2 11% 2CyPhPh5O2 10% 3CyPhPh5O2 11% 3PhPh5Ph2  5% 4PhPh5Ph2  6% T_(NI)/° C. 75.9 Δn 0.104 n_(o) 1.483 Δε −3.06 ε_(⊥) 6.56 η/mPa · s 19.9 γ₁/mPa · s 137 γ₁/Δn² × 10⁻³ 12.7 γ₁/Δn²/|Δε| 4.14

It is understood that the liquid-crystal composition 4 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. An FFS mode liquid-crystal display element was prepared using the liquid-crystal composition 4, and this exhibited excellent display characteristics comparable to Examples 1 to 3.

Example 5 Liquid-Crystal Composition 5

A liquid-crystal composition (liquid-crystal composition 5) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 1 to 4, to was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 8 Example 5 3CyCy2 25% 3CyCy4 10% 3CyCy5  5% 3CyPh5O2  8% 3PhPh5O2  9% 3CyCyPh5O2 12% 4CyCyPh5O2  2% 2CyPhPh5O2  9% 3CyPhPh5O2  9% 3PhPh5Ph2  5% 4PhPh5Ph2  6% T_(NI)/° C. 75.8 Δn 0.108 n_(o) 1.485 Δε −3.17 ε_(⊥) 6.53 η/mPa · s 18.5 γ₁/mPa · s 131 γ₁/Δn² × 10⁻³ 11.2 γ₁/Δn²/|Δε| 3.54

It is understood that the liquid-crystal composition 5 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. An FFS mode liquid-crystal display element was prepared using the liquid-crystal composition 5, and this exhibited excellent display characteristics comparable to Examples 1 to 3.

Example 6 Liquid-Crystal Composition 6

A liquid-crystal composition (liquid-crystal composition 6) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 1 to 5, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 9 Example 6 3CyCy2 25% 3CyCy4 10% 3CyCy5  6% 3CyCyPh1 10% 3CyPh5O2  5% 3PhPh5O2 10% 5PhPh5O2  4% 3CyCyPh5O2  6% 2CyPhPh5O2 12% 3CyPhPh5O2 12% T_(NI)/° C. 78.1 Δn 0.101 n_(o) 1.484 Δε −3.00 ε_(⊥) 6.22 η/mPa · s 15.9 γ₁/mPa · s 111 γ₁/Δn² × 10⁻³ 10.9 γ₁/Δn²/|Δε| 3.63

It is understood that the liquid-crystal composition 6 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. An FFS mode liquid-crystal display element was prepared using the liquid-crystal composition 6, and this exhibited excellent display characteristics comparable to Examples 1 to 3.

Example 7 Liquid-Crystal Composition 7

A liquid-crystal composition (liquid-crystal composition 7) having the compositional ratio described below, which was designed to have the same Δn value as and a higher T_(NI) and a greater Δ∈ value than the liquid-crystal compositions 1 to 6 was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 10 Example 7 3CyCyV 24% 3CyCyV1 10% 3CyPh5O2 12% 5CyPh5O2  8% 3CyCyPh5O2 10% 3CyCyPh5O3  8% 4CyCyPh5O2 10% 2CyPhPh5O2  5% 3CyPhPh5O2  5% 3PhPh5Ph2  8% T_(NI)/° C. 86.0 Δn 0.103 n_(o) 1.481 Δε −3.95 ε_(⊥) 7.76 η/mPa · s 21.8 γ₁/mPa · s 134 γ₁/Δn² × 10⁻³ 12.6 γ₁/Δn²/|Δε| 3.20 Initial voltage holding ratio/% 99.9 Voltage holding ratio at 150° C. after 1 hour/% 99.4 Burn-in evaluation A Drip mark evaluation A Process adaptability evaluation A Solubility evaluation at low temperature A

It is understood that the liquid-crystal composition 7 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 7, an FFS mode liquid-crystal display element was prepared in the same manner as in Example 1, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Example 8 Liquid-Crystal Composition 8

A liquid-crystal composition (liquid-crystal composition 8) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as that of the liquid-crystal composition 7, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 11 Example 8 3CyCyV 20% 3CyCyV1 10% 3CyCyPh1  7% 3CyPh5O2 12% 5CyPh5O2  6% 3PhPh5O2  5% 3CyCyPh5O2 12% 3CyCyPh5O3  6% 4CyCyPh5O2 10% 2CyPhPh5O2  6% 3PhPh5Ph2  6% T_(NI)/° C. 85.6 Δn 0.103 n_(o) 1.482 Δε −4.05 ε_(⊥) 7.74 η/mPa · s 21.2 γ₁/mPa · s 128 γ₁/Δn² × 10⁻³ 12.1 γ₁/Δn²/|Δε| 2.98 Initial voltage holding ratio/% 99.9 Voltage holding ratio at 150° C. after 1 hour/% 99.5 Burn-in evaluation A Drip mark evaluation A Process adaptability evaluation A Solubility evaluation at low temperature A

It is understood that the liquid-crystal composition 8 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 8, an FFS mode liquid-crystal display element was prepared in the same manner as in Example 1, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Example 9 Liquid-Crystal Composition 9

A liquid-crystal composition (liquid-crystal composition 9 having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 7 and 8, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 12 Example 9 3CyCyV 23% 3CyCyV1 10% 3CyCyPh1 10% 3CyPh5O2 10% 5CyPh5O2  4% 3PhPh5O2  8% 3CyCyPh5O2 12% 4CyCyPh5O2  7% 2CyPhPh5O2  8% 3CyPhPh5O2  8% T_(NI)/° C. 86.2 Δn 0.103 n_(o) 1.483 Δε −3.96 ε_(⊥) 7.56 η/mPa · s 18.7 γ₁/mPa · s 112 γ₁/Δn² × 10⁻³ 10.6 γ₁/Δn²/|Δε| 2.67 Initial voltage holding ratio/% 99.8 Voltage holding ratio at 150° C. after 1 hour/% 99.3 Burn-in evaluation A Drip mark evaluation A Process adaptability evaluation A Solubility evaluation at low temperature A

It is understood that the liquid-crystal composition 9 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 9 an FFS mode liquid-crystal display element was prepared in the same manner as in Example 1, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Comparative Examples 4 to 6

VA mode liquid-crystal display elements were prepared using the liquid-crystal compositions 7 to 9 in the same manner as in each of Comparative Examples 1 to 3.

Comparisons of transmittances, contrast ratios, response speeds were performed on the FFS mode liquid-crystal display element prepared in each of Examples 7 to 9 and the VA mode liquid-crystal display element prepared in each of Comparative Examples 4 to 6. The results are shown below.

TABLE 13 Comparative Comparative Comparative Example 7 Example 4 Example 8 Example 5 Example 9 Example 6 Display mode n-FFS VA n-FFS VA n-FFS VA Liquid-crystal Liquid-crystal Liquid-crystal Liquid-crystal composition composition 7 composition 8 composition 9 used Maximum 88% 85% 88% 86% 89% 87% transmittance/% Contrast ratio 278 268 285 265 294 260 Response speed/ 7.4 13.0 7.1 12.7 6.5 10.8 ms

The FFS mode display elements prepared using the liquid-crystal compositions 7 to 9 (Examples 7 to 9) exhibit characteristics excellent in the maximum transmittance, the contrast ratio, and the response speed, compared to each of VA mode liquid-crystal display elements (Comparative Examples 4 to 6) prepared using the same liquid-crystal composition, respectively.

Example 10 Liquid-Crystal Composition 10

A liquid-crystal composition (liquid-crystal composition 10) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 7 to 9, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 14 Example 10 3CyCy2 22% 3CyCy4  4% 3CyCyPh1  4% 3CyPh5O2 12% 5CyPh5O2 10% 3CyCyPh5O2 10% 3CyCyPh5O3  6% 4CyCyPh5O2  9% 2CyPhPh5O2  8% 3CyPhPh5O2  8% 3PhPh5Ph2  4% 4PhPh5Ph2  3% T_(NI)/° C. 85.7 Δn 0.103 n_(o) 1.482 Δε −4.08 ε_(⊥) 7.92 η/mPa · s 26.6 γ₁/mPa · s 172 γ₁/Δn² × 10⁻³ 16.2 γ₁/Δn²/|Δε| 3.97

It is understood that the liquid-crystal composition 10 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 10, an FFS mode liquid-crystal display element was prepared, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature ware evaluated in the same manner described above, the evaluation results were excellent.

Example 11 Liquid-Crystal Composition 11

A liquid-crystal composition having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 7 to 10, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 15 Example 11 3CyCy2 24% 3CyCy4  8% 3CyPh5O2  9% 3PhPh5O2  8% 3CyCyPh5O2 12% 3CyCyPh5O3 10% 4CyCyPh5O2 10% 2CyPhPh5O2  6% 3CyPhPh5O2  6% 3PhPh5Ph2  4% 4PhPh5Ph2  3% T_(NI)/° C. 86.0 Δn 0.103 n_(o) 1.483 Δε −4.03 ε_(⊥) 7.67 η/mPa · s 24.3 γ₁/mPa · s 164 γ₁/Δn² × 10⁻³ 15.5 γ₁/Δn²/|Δε| 3.84

It is understood that the liquid-crystal composition 11 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 11, an FFS mode liquid-crystal display element was prepared, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Example 12 Liquid-Crystal Composition 12

A liquid-crystal composition (liquid-crystal composition 12) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 7 to 11, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 16 Example 12 3CyCy2 24% 3CyCy4  5% 3CyCyPh1  9% 3CyPh5O2 10% 5CyPh5O2  3% 3PhPh5O2  8% 3CyCyPh5O2 10% 4CyCyPh5O2  9% 2CyPhPh5O2 11% 2CyPhPh5O2 11% T_(NI)/° C. 86.0 Δn 0.103 n_(o) 1.484 Δε −4.03 ε_(⊥) 7.69 η/mPa · s 22.5 γ₁/mPa · s 145 γ₁/Δn² × 10⁻³ 13.7 γ₁/Δn²/|Δε| 3.39

It is understood that the liquid-crystal composition 12 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 12, an FFS mode liquid-crystal display element was prepared, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature ware evaluated in the same manner described above, the evaluation results were excellent.

Example 13 Liquid-Crystal Composition 13

A liquid-crystal composition (liquid-crystal composition 13) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 7 to 12, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 17 Example 13 3CyCyV 20% 3CyCyV1 10% 3CyCyPh1  7% 3CyPhPh2  3% 3CyPh5O2 13% 5CyPh5O2 12% 3CyCyPh5O2 10% 4CyCyPh5O2  5% 2CyPhPh5O2 10% 3CyPhPh5O2 10% T_(NI)/° C. 85.8 Δn 0.103 n_(o) 1.482 Δε −4.02 ε_(⊥) 7.82 η/mPa · s 20.9 γ₁/mPa · s 123 γ₁/Δn² × 10⁻³ 11.7 γ₁/Δn²/|Δε| 2.88

It is understood that the liquid-crystal composition 13 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 13, an FFS mode liquid-crystal, display element was prepared in the same manner as in Example 1, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

Example 14 Liquid-Crystal Composition 14

A liquid-crystal composition (liquid-crystal composition 14) having the compositional ratio described below, which was designed to have the same T_(NI), the same Δn value, and the same Δ∈ value, as those of the liquid-crystal compositions 7 to 13, was prepared, and the physical properties thereof were measured. The results are shown in the following Table.

TABLE 18 Example 14 3CyCy2 22% 3CyCy4  3% 3CyCyPh1  7% 3CyCyPh2  4% 3CyPh5O2 13% 5CyPh5O2 12% 3CyCyPh5O2  9% 4CyCyPh5O2  6% 2CyPhPh5O2 12% 3CyPhPh5O2 12% T_(NI)/° C. 85.0 Δn 0.103 n_(o) 1.483 Δε −4.04 ε_(⊥) 7.88 η/mPa · s 24.3 γ₁/mPa · s 152 γ₁/Δn² × 10⁻³ 14.3 γ₁/Δn²/|Δε| 3.55

It is understood that the liquid-crystal composition 14 has a T_(NI) which is practical as a liquid-crystal composition for a TV, a great absolute value of Δ∈, and a low η and an optimal Δn. Using the liquid-crystal composition 14, an FFS mode liquid-crystal display element was prepared in the same manner as in Example 1, and when the burn-in, the drip marks, the process adaptability, and the solubility at low temperature were evaluated in the same manner described above, the evaluation results were excellent.

REFERENCE SIGNS LIST

1,8 POLARIZING PLATE

2 FIRST SUBSTRATE

3 ELECTRODE LAYER

4 ALIGNMENT FILM

5 LIQUID-CRYSTAL LAYER

6 COLOR FILTER

7 SECOND SUBSTRATE

11 GATE ELECTRODE

12 GATE INSULATING FILM

13 SEMICONDUCTOR LAYER

14 INSULATING LAYER

15 OHMIC CONTACT LAYER

16 DRAIN ELECTRODE

17 SOURCE ELECTRODE

18 ISOLATION PROTECTING LAYER

21 PIXEL ELECTRODE

22 COMMON ELECTRODE

23 STORAGE CAPACITOR

25 DATA BUS LINE

27 SOURCE BUS LINE

29 COMMON LINE 

The invention claimed is:
 1. A FFS mode liquid-crystal display device, comprising: a first substrate and a second substrate disposed to face each other; a liquid-crystal layer containing a liquid-crystal composition with which a gap between the first substrate and the second substrate is filled; an electrode layer including a common electrode including a transparent conductive material, a plurality of gate bus lines and data bus lines disposed in a matrix shape, a thin film transistor provided at the intersection at which the gate bus lines and the data bus lines intersect each other, and a pixel electrode including a transparent conductive material and forming a fringe electric field between the common electrode and the pixel electrode by being driven by the thin film transistor, for each pixel on the first substrate; and photo-alignment film layers inducing homogeneous alignment which are formed between the liquid-crystal layer and the first substrate and between the liquid-crystal layer and the second substrate, respectively, wherein a distance R between the pixel electrode and the common electrode is smaller than a distance G between the first substrate and the second substrate, and the liquid-crystal composition has a negative dielectric anisotropy, a nematic phase-isotropic liquid transition temperature of equal to or higher than 60° C., and an absolute value of dielectric anisotropy of equal to or greater than 2, and contains at least two compounds represented by the following General Formula (I):

wherein each of R¹ and R² independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, A represents a trans-1,4-cyclohexylene group, k represents 1, and at least one compound represented by General Formula (II)

wherein R³ represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, R⁴ represents an an alkoxy group having 1 to 8 carbon atoms, B represents a 1,4-phenylene group, m represents
 1. 2. The FFS mode liquid-crystal display device according to claim 1, wherein the liquid-crystal composition contains at least one represented by the following General Formula (IV):

wherein each of R⁷ and R⁸ independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, one or more hydrogen atoms in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with a fluorine atom, any methylene group in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with an oxygen atom as long as the oxygen atom is not continuously bonded to another oxygen atom or may be substituted with a carbonyl group as long as the carbonyl group is not continuously bonded to another carbonyl group, each of A¹ and A¹ independently represents a 1,4-cyclohexylene group, a 1,4-phenylene group, or a tetrahydropyran-2,5-diyl group, in a case where A¹ or/and A¹ represent a 1,4-phenylene group, one or more hydrogen atoms in the 1,4-phenylene group may be substituted with a fluorine atom, each of Z¹ and Z² independently represents a single bond, —OCH₂—, —OCF₂—, —CH₂O—, or CF₂O—, each of n¹ and n² independently represents 0, 1, 2, or 3, n¹ +n² is 1 to 3, and in a case where a plurality of A¹'s, A²'s, Z¹'s, and/or Z²'s are present, these may be the same as or different from each other, with the proviso that a compound in which n¹ is 1 or 2, n² is 0, at least one of A¹'s is a 1,4-cyclohexylene group, and all Z¹'s are single bonds is excluded.
 3. The FFS mode liquid-crystal display device according to claim 1, comprising: at least one compound represented by the following General Formula (III) as the compound represented by General Formula (I):

wherein R⁵ represents a hydrogen atom or a methyl group, and R⁶ represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms.
 4. The FFS mode liquid-crystal display device according to claim 2, comprising: at least one compound selected from the group consisting of compounds represented by the following General Formula (IVa1) or the following General Formula (IVa2) as the compound represented by General Formula (IV):

wherein each of R^(7a1), R^(7a2), R^(8a1), and R^(8a2) independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, one or more hydrogen atoms in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with a fluorine atom, any methylene group in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with an oxygen atom as long as the oxygen atom is not continuously bonded to another oxygen atom or may be substituted with a carbonyl group as long as the carbonyl group is not continuously bonded to another carbonyl group, n^(a2) represents 0 or 1, A^(1a2) represents a 1,4-cyclohexylene group, a 1,4-phenylene group, or a tetrahydropyran-2,5-diyl group, and one or more hydrogen atoms in 1,4-phenylene group present in General Formulas (IVa1) and (IVa2) may be substituted with a fluorine atom.
 5. The FFS mode liquid-crystal display device according to claim 1, wherein the pixel electrode has a comb shape or a slit.
 6. The FFS mode liquid-crystal display device according to claim 1, wherein the distance (R) between the electrodes is 0, and the common electrode is formed on almost the entire surface of the first substrate and disposed at a position closer to the first substrate than the pixel electrode.
 7. The FFS mode liquid-crystal display device according to claim 1, wherein the photo-alignment film is at least one selected from the group consisting of a photoresponsive decomposition type polymer, a photoresponsive dimerization type polymer, and a photoresponsive isomerization type polymer.
 8. The FFS mode liquid-crystal display device according to claim 1, further comprising at least one compound represented by the following General Formula (I):

wherein each of R¹ and R² independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, A represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group, k represents 1 or 2, and in a case where k is 2, two A's may be the same as or different from each other, and excluding a compound wherein when k is 1, and A is a trans-1,4-cyclohexylene group.
 9. The FFS mode liquid-crystal display device according to claim 8, further comprising at least one compound represented by General Formula (II)

wherein R³ represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, R⁴ represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms, B represents a 1,4-phenylene group or a trans-1,4-cyclohexylene group, m represents 0, 1, or 2, and in a case where m is 2, two B's may be the same as or different from each other, and excluding a compound wherein when m is 0, B is a 1,4-phenylene group and R⁴ represents an alkoxy group having 1 to 8 carbon atoms.
 10. The FFS mode liquid-crystal display device according to claim 9 wherein the total content of the compounds represented by General Formula (I) and (II) in the liquid crystal composition is 55% by mass to 95%.
 11. The FFS mode liquid-crystal display device according to claim 9, wherein the liquid-crystal composition contains at least one represented by the following General Formula (IV):

wherein each of R⁷ and R⁸ independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, one or more hydrogen atoms in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with a fluorine atom, any methylene group in the alkyl group, the alkenyl group, the alkoxy group, or the alkenyloxy group may be substituted with an oxygen atom as long as the oxygen atom is not continuously bonded to another oxygen atom or may be substituted with a carbonyl group as long as the carbonyl group is not continuously bonded to another carbonyl group, each of A¹ and A¹ independently represents a 1,4-cyclohexylene group, a 1,4-phenylene group, or a tetrahydropyran-2,5-diyl group, in a case where A¹ or/and A¹ represent a 1,4-phenylene group, one or more hydrogen atoms in the 1,4-phenylene group may be substituted with a fluorine atom, each of Z¹ and Z² independently represents a single bond, —OCH₂—, —OCF₂—, —CH₂O—, or CF₂O—, each of n¹ and n² independently represents 0, 1, 2, or 3, n¹+n² is 1 to 3, and in a case where a plurality of A¹'s, A²'s, Z¹'s, and/or Z²'s are present, these may be the same as or different from each other, with the proviso that a compound in which n¹is 1 or 2, n² is 0, at least one of A¹'s is a 1,4-cyclohexylene group, and all Z¹'s are single bonds is excluded.
 12. The FFS mode liquid-crystal display device according to claim 11, wherein the total content of the compounds represented by General Formula (I), (II) and (IV) in the liquid crystal composition is 97% by mass to 100%. 